It may have been temporary files that should have been deleted. Click properties of each one to find what each is for.
I have Windows XP Home Edition OEM 2002 and there isn't a Windows/installer in my computer. I have in Program Files 2, AOL and Quicktime. DotNetInstaller, 2 in Common Files; Documents and Settings/<my name> are 2, QTInstallerHelper.dll & WindowsInstaller-KB893803-v2-x86 & RealPlayer Uninstaller in All Users (1).
If you have IE6 SP1 or SP2, you may find many under: Cookies, click Index.dat and delete the rest thru Edit and Invert Selection.
History has various days on your computer unless you set it to zero in Internet Options, Right click, select Edit and delete them all except History.
Temporary Internet Files, Edit, Select All and delete.
You nay have a lot of My Recent Documents (Recent) highlight it by clicking on all the files, listed above, Edit, Select All.
I set History to 0 & Temp Internet files to 10 MB.
Disk Cleanup-Compressed files, click on it and there is Options, it was 50 days and it is set at 1 day, go past it and it will be in the 500's , go back to 1 day and click OK. Eventually, you will see no compressed files in a week. Darrell L.