When XP lays out its directories structure as follows:
Documents and Settings #1
Program Files
Windows

So, does Windows 7, but slightly different naming:
Users <--- softlink to #1
Program Files #2
ProgramData <--- configuration of #2
Windows

To reinstall Windows 7 or fresh install over old Windows 7, it will gather all old content of Windows folder and dump it into Windows.OLD; disk space sucker wacko.gif .

Have you heard of ExplorerXP that help erase easily thumbup.gif ? A Google Search brings to `ExplorerXP is a very fast, small, compact and innovative FREEWARE (for non - commercial use) file ... Download http://www.explorerxp.com/explorerxpsetup.exe - 410 KB. Version 1.07`

How it works simply by renaming the folder name with file extension,
e.g. changed ProgramFiles to ProgramFiles.old

In this sequence of renaming and deletion,
i.e. Windows.old, ProgramData.old, ProgramFiles.old, Users.old, Documents and Settings.old (softlink), Perflog.old (optional), Recovery.old (optional)

Remember to set 0% in Recycle Bin, or press Shf + Del while deleting them permanently safe and sound

Note that the filesize of DirSizeCache.dat, FolderStates.dat, and Groups.dat within ExplorerXP folder will gradually increase, especially the FolderStates.dat, which is safe to delete it when the program exits (optional).