Help ,I cant use checkdisk on my win xp [C:\] drive[NTFS]

Help!!,I cant use checkdisk to scan for errors on my Win XP Pro
PC as whenever I try to do so or schedule a test and restart...I get the
following error.....[cannot open volume for access] and then checkdisk
says that the test is finished.

The problem started when I converted my FAT32 file system to NTFS
using the internal command prompt command.So no matter how many errors my [C:\] drive contains I just cant scan it even before XP loads..
as all I fet to see is that the volume cannot be accessed.

However my other partition [D:\] drive which is FAT32 has no such problem.....I can peacefully use checkdisk on it and rectify filesystem errors. SOMEONE PLZ ADVICE AS TO HOW I CAN GET CHECKDISK TO
SCAN MY C DRIVE.....HEEEELLLLLPPPPP!!!!!