I guess there are already threads dedicated to this subject - which files and folders you can safely delete from a Windows XP partition without having any problem. Unfortunately I cant'd find them ...

Warnings While removing a drive letter for a network drive or virtual drive doesn't delete any files, it may cause errors in applications that try to retrieve a file using the deleted drive letter.

How to Reload Windows XP Without Removing Files. Deleting system files, modifying the registry and installing incompatible drivers to Windows XP can damage the integrity of the operating system ...

AVG Anti-Virus 8 Anti-Virus 8 is a free antivirus program that is compatible with various Windows systems, including Windows 2000, Windows XP, Windows XP Pro x64, Windows Vista, and Windows Vista x64.

Windows won't let you delete, move, or rename a file if a program is using it. Frustratingly, it also won't tell you which program is using the file so that you can solve the problem.