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Back Up your Data and settings before Upgrade

Having an up-to-date backup of important files is, of course, good advice for any time. But it's especially important when you're upgrading an operating system.

The simplest way to back up files is to sync them to the cloud. OneDrive sync capabilities are built in to Windows 8.1; a sync utility for Windows 7 is available for download from http://onedrive.com/download. Move or copy your files into the OneDrive folder and wait for them to be fully synchronized before proceeding.

With large file collections or slow Internet connections, a sufficiently large USB flash drive or an external hard drive makes a perfectly good target for a local backup. If you're upgrading from Windows 7, you can use its built-in backup program; individual files and folders from those backups can be restored in Windows 10 by using the helpfully labeled Backup And Restore (Windows 7) option.

If you're upgrading from Windows 8.1 and you've signed in with a Microsoft account, your personalized settings are already being synced to OneDrive. From Windows 7, there's no easy way to back up those settings. Although you can find third-party utilities that promise to accomplish this task, it's probably faster (and less risky) to re-create that handful of settings than it is to mess with transfer utilities.

Choose the right package

Those who are able to upgrade online can skip this section. The Windows 10 installer delivered through Windows Update chooses the correct successor to your current edition, downloads it for you in the background, and then walks you through setup.

But for every other Windows 10 installation scenario, you have some decisions to make. To do a clean install or to upgrade using Windows media, you typically download an ISO file, which you can then mount directly or use to create installation media. (Physical copies of Windows 10 are also available in packages in which the installer is on a bootable USB flash drive or a DVD.)

The ISO name is ancient, by modern computing standards, dating back to the mid-1980s. And, strictly speaking, it's also meaningless. The name is shorthand for the file system originally used with CD-ROM media, which was designated ISO 9660 by the standards-setting body that published it. These days, an ISO image file is just as likely to use the UDF file system (ISO/IEC 13346), which is commonly found on larger-capacity optical media such as DVDs and Blu-ray Discs.

Choosing the correct installer involves finding the specific combination of three factors that match your needs:

  • Windows 10 edition
    For installing or upgrading a desktop PC, laptop, or hybrid device, there are two and only two choices: Windows 10 Home or Windows 10 Pro. (Large organizations with volume license contracts can install Windows 10 Enterprise as an upgrade.)
  • Language
    Windows 10 is available in a large number of languages-111 languages, covering 190 countries and regions, at the time of its initial release. Choose the base language that is appropriate for your installation. You can add language interface packs to translate text that's displayed in commonly used wizards, dialog boxes, menus, and other items in the user interface; however, you can't change the parent language except by reinstalling Windows using an edition built for that language.
  • Architecture
    Windows 10 is available in 32-bit and 64-bit distributions. Most modern CPUs will support either version, and your preference should be for the 64-bit version. In general, 32-bit versions of Windows are appropriate for systems with 2 GB (or less) of RAM, with no option to add memory. Choose a 64-bit version if your system includes 4 GB or more of memory or if you rely on one or more programs that are available only in 64-bit editions. (And note that all of your 32-bit programs, including new and old versions of Microsoft Office, will work fine on a 64-bit copy of Windows, so you needn't fear in that regard.)

If your goal is to purchase a physical or electronic copy of Windows for installation on a new PC or in a virtual machine, the intricacies of Windows licensing require several additional decisions beyond those we just described.

You can choose from the following license types:

  • Full.
    A full license is sold directly to consumers as an electronic distribution or a packaged product. With a full license, Windows can be installed on a computer that was not sold with Windows originally, or it can be used as an upgrade. A full license can be transferred to a different computer as long as the underlying copy of Windows is no longer being used on the original location.
  • OEM.
    An OEM (original equipment manufacturer) license is one that's included with a new computer. This license is locked to the computer on which it's installed and cannot be transferred to a new computer. OEM System Builder packages are intended for use by small PC makers but are often used by consumers and hobbyists in place of a full license. The system builder is required to provide support for OEM Windows along with the device on which it is installed.
  • Upgrade.
    An upgrade license is a discounted copy of Windows that can be installed only on a system that already has an OEM or full license.
  • Volume.
    Volume licenses are sold in bulk to corporate, government, nonprofit, and educational customers and are typically deployed by using enterprise management tools. A volume license is available as an upgrade only.

Any PC that was purchased with Windows 7, Windows 8, or Windows 8.1 preinstalled (look for the sticker on the PC itself or on the power supply) is qualified for a free Windows 10 upgrade (the free upgrade offer is good until July 29, 2016). This is true whether the PC came from a large OEM or from a system builder.

You need a full license to install Windows in a virtual machine, on a Mac or other computer that does not come with Windows preinstalled, or in a dual-boot or multiboot setup. That condition can be satisfied with a full (retail or OEM) license of Windows 10 or a full license for an earlier Windows version that supports a Windows 10 upgrade.

It's important to understand that the legal and contractual restrictions imposed by license agreements are completely independent of technical restrictions on installation. If you upgrade a system to Windows 10 from Windows 7 and then the system's hard disk fails, you can perform a clean install of Windows 10 and still be properly licensed. Conversely, it is technically possible to install and activate an upgrade version on a computer that doesn't have an underlying license, but doing so violates the license agreement.

Choose your upgrade method

Microsoft strongly encourages online upgrades for anyone running Windows 7 (with Service Pack 1) or Windows 8.1. But you also have the option to perform a custom installation. A custom installation of Windows 10 allows you to start from scratch, with or without your personal data files; you need to reinstall your programs and re-create or transfer settings from another system. An upgrade retains installed programs and settings, but at the risk of creating some compatibility issues.

You'll need to boot from the Windows 10 media and choose a custom installation if either of the following conditions is true:

  • You need to adjust the layout of the system disk. The Windows 10 installation program includes disk-management tools that you can use to create, delete, format, and extend (but not shrink) partitions on hard disks installed in your computer. Knowing how these tools work can save you a significant amount of time when setting up Windows.
  • You want to install Windows 10 alongside another operating system. If you want to set up a multiboot system, you'll need to understand how different startup files work so that you can manage your startup options effectively.

If the system on which you plan to install Windows 10 is already running Windows 7, Windows 8.1, or Windows 10, you can start the setup program from within Windows.

Running setup from within Windows allows you to upgrade from Windows 7 or Windows 8.1, transferring settings and desktop programs to the new installation-provided that the Windows 10 edition is equivalent to or higher than the currently installed Windows edition. If you attempt an unsupported upgrade path, you have the option to transfer personal files only. Table shows the supported upgrade paths.

Current version		 Supported upgrade
Windows 7 Starterm 	Windows 10 Home
Home Basic,
Home Premium

Windows 7 	 	Windows 10 Pro

Windows 8.1		Windows 10 Home

Windows 8.1 Pro, 	Windows 10 Pro
Windows 8.1
Pro for Students

Windows Phone 8.1	Windows 10 Mobile

Starting Setup from within Windows does not offer the option to perform a custom install. However, performing an upgrade and choosing Nothing from the list of what you want to keep has the same effect as performing a clean install. After Windows 10 is installed, the Reset option is the preferred way to accomplish the task of repairing a Windows installation that isn't working properly.

Note that the installation media must match the architecture of the installed Windows version. You cannot run the 64-bit setup program on a PC running a 32-bit version of Windows, or vice versa. In addition, you cannot make any changes to the layout of a disk when running Setup from within Windows; you must use existing partitions, and Setup will not recognize or use unallocated space on an attached hard drive.

If you boot from the Windows 10 installation media, you can delete existing partitions, create new partitions, extend an existing disk partition to unallocated space, or designate a block of unallocated space as the setup location. After booting from the Windows installation media, you cannot upgrade an existing Windows installation. Your only option is a custom install.

Using either setup option, you can install Windows 10 on the same volume as an existing Windows version.

In the next section, we explain what happens behind the scenes when you perform a Windows 10 upgrade or a clean install.

How Windows 10 Setup works

The Windows 10 setup program does its magic using two folders.

  • C:\$Windows.~BT is a hidden folder that contains the files used during both the online and offline phases of setup. These files are downloaded directly if you upgrade using Windows Update. When you launch Setup from installation media, such as an ISO file or a bootable DVD or USB flash drive, the initial phase of setup creates this folder and copies the setup files to it for temporary use, eliminating the possibility of a setup failure caused by prematurely removing or unmounting the installation media.
  • C:\Windows.old is created only when you perform an upgrade or do a clean install on a volume that already contains a Windows installation. This folder does double duty. During upgrades, it's used as a transfer location to hold files and settings that are moving from the old installation to the new one. After setup is complete, this folder holds system files from the previous Windows installation as well as any user files that were not migrated during setup.
These temporary installation files are deleted automatically after four weeks. Your previous Windows installation is saved indefinitely in Windows.old, allowing you to roll back to the previous version if necessary. On systems with limited storage, you can use the Disk Cleanup utility to remove these files manually.