chkdsk /f error when running defragmenter in XP tablet edition

I am running win xp tablet edition 2005 and have tried to run disk defragmenter but got the message: Disk Defragmenter has detected that Chkdsk is scheduled to run on the volume: (C:). Please run Chkdsk /f.

I did (start – run – chkdsk)and get the message: Chkdsk cannot run becuase the volume is in use by another process. Would you like to schedule this volume to be checked the next time the system restarts? . I type Y and reboot the machine. The next time i run deframenter, i get the same message.

Next i tried to run chkdsk from safemode w/ prompt and got the same message as before. No matter what i try, i can’t solve the issue.

Please help.