It sounds like you are trying to run Norton Disc Doctor, yes?
This is from the Symantec Knowledge Base:
"The operating system or another process currently has exclusive access to this drive or some of its files. Norton Disk Doctor cannot continue with a repair under these conditions. A repair can be scheduled to occur the next time you restart the system. Norton Disk Doctor can still diagnose this drive if 'Fix Errors' is unchecked. Would you like to schedule a repair?"
Because of the way Windows 2000 and Windows XP operate with hardware devices, there is no way for Norton Disk Doctor to repair the C: drive while Windows is running. In order for Norton Disk Doctor to obtain exclusive access to the C: drive, you must click "Yes" on the message box that asks "Would you like to schedule a repair?" After doing this, Windows will run CheckDisk to repair the drive the next time you restart the computer.
Windows XP does not have scandisk anymore, it uses CheckDisk instead and Norton Disc Doctor cannnot be used while Windows is running. You can only use it in a DOS session.