Cannot run Norton Disk doctor on winxp

when i run Norton disk doctor on win xp professional with the FIX ERROR AUTOMATICALLY option checked it gives me an error” The operating system or another process has exclusive rights to this drive or some files. norton cannot continue with repair under this condition”.Even running the error check from win xp gives an error when FIX ERROR AUTOMATICALLY option is checked. Please help as my disk free space is not being reported properly.