Four days ago I updated my computer from Windows Vista to Windows 7 Pro only I didn't format my C drive so now only 1% of my system memory is available. Is there a way that I can remove Vista and reinstall Windows 7 Pro so that my C drive is freed up?
Check for a Windows.old File
It depends. Did you perform the upgrade as an "in-place" upgrade or a custom install? An in-place install means that all of your existing applications, data, documents, and other settings remain in place after the upgrade. A custom install involves installing Windows from scratch, losing all your programs and data in the process. Depending on the version of Windows your computer original had, you may not have a choice because some versions of Windows XP and Vista do not support in-place upgrades.
If you did a custom install, then there should be a folder named "Windows.old" on your C drive. Even though the custom installation wipes your disk clean, it creates a folder containing old system and personal files. This folder can take up large amounts of disk space. As long as you're confident that your new Windows 7 installation is stable, you can delete this folder. Before you do, take a look at this Microsoft Knowledge Base article detailing how to restore your personal files after a custom install. This is handy if you need to recover your documents, programs, and other data.
Deleting the Windows.old File
To delete this folder, use the Disk Cleanup Wizard. Using the Disk Cleanup Wizard is relatively easy. Go to Start and type in "Disk Cleanup." You'll see an icon appear. Click that icon and go to the Disk Cleanup tab. Find and choose the "Clean up system files" option. You'll likely be prompted to specify the drive where these files are located. Next, select the "Previous installation" option as well as any other files that you'd like to delete at the same time and then click OK followed by Delete Files.
Remember, this process cannot be undone, so make sure you're completely confident that the Windows 7 upgrade is stable.