Microsoft offers several paths to install Windows 7. You can upgrade from Windows XP or Vista, or do a clean install on your computer. The clean install process took us exactly 18 minutes on a modestly spec-ed machine and it has been our fastest experience right from Windows 3.1 to a bloated Windows Vista.
The upgrade procedure is different depending on whether you're currently running Windows XP or Windows Vista. Windows 7 provides a direct upgrade path to Windows 7 from Vista. This means that when you install Windows 7, all you need to do is select the Upgrade option during Windows 7 installation. Note: Windows 7 requires that you've installed Vista Service Pack 1 over your base Vista installation in order to upgrade.
Unfortunately, Windows 7 doesn't provide a direct Upgrade path for Windows XP users, and you have to go through the whole process of backing up your data, formatting and installing Windows, and then restoring your files and settings using the 'User State Migration Tool' which moves all your desktop, application and system settings apart from your files to a new Windows installation. It is kind of like Microsoft's punishment for skipping Vista, but Microsoft has made sure not to alienate XP users and they've provided a series of videos detailing how to migrate from XP to Windows 7 on their website.
Let us get down to installing Windows. What are your options?
You've two options from the default installer:
Upgrade to Windows 7 – This option upgrades your current operating system and keeps your files, settings and programs as they are presently.
Install Windows by performing a custom installation – This option is used to completely replace your current operating system, or to install Windows on a separate partition for multi-boot. This is your only choice if your computer does not have any operating system. This option also gives you advanced Disk Management features such as Format, Extend partition, Create or Delete partition if you have booted your computer using the Windows Installation Disc and not using the setup.exe from your existing Windows installation A custom installation does not retain any of your programs or settings. If you delete or formatted the partition that holds your current Operating system, all data on that partition, including programs, files and settings would be permanently deleted once you go with the installation process. However if you decide not to format or delete the Windows partition and install Windows 7 on top of it, all your user files will be saved in a 'Windows.old' folder automatically on the same partition. While this does not delete your previous files, your encrypted files will be rendered useless in the new Windows. So, we recommend you to back them up before performing a Custom Install. You can delete the ‘Windows.old’ folder using Disk Cleanup Utility on your Windows partition.