If you install Windows 7 by performing a custom installation, instead of formatting the partition during Setup, the files used in previous versions of Windows are stored in the Windows.old folder. The type of file in this folder depends on your computer. Once you have reached a certain time using Windows 7, if you are confident that your files and settings have returned to where you want them to be, you can safely reclaim disk space by using Disk Cleanup to remove the Windows.old folder.
- Open Disk Cleanup by clicking the Start button. In the Search box, type Disk Cleanup, and then click Disk Cleanup in the results list. If you are prompted to select a drive, click the drive that installs Windows, and then click OK.
- In the Disk Cleanup dialog box, on the Disk Cleanup tab, click Clean System files. If the system prompts you to select the drive again, click the drive that installs Windows, and then click OK.
- Select the previous Windows installation check box, and any additional check boxes that correspond to the files you want to delete, and then click OK.
- In the message that appears, click Delete File.