Creating space on C partition

"Three simple options:

Use the disk cleanup as described in the other answers.
A simple other solution is moving some old (archived) files to the D drive.
Delete some unused programs: control panel->add or remove programs

You can remove old users from Control panel->user accounts
After you've removed them, check the ""C:/documents and settings/"" folder. There you can remove all old user folders. (NOTE: all documents stored under those users will be removed, make sure you won't need those for your work, or have them backed-up)"

You can right click the disk drive in My Computer select Properties, Tools, Disk Cleanup. That is safe.

"The c:\windows\options is used by System Restore to store pristine copies of system files. It can be removed if you have all drivers supplied by the OEM manufacturer and the Windows XP setup files stored somewhere.

If you're absolutely sure that your coworkers haven't forgotten any important files on your computer, then you can delete the profiles as well. If in doubt, make a backup before deleting anything."