WIN2K chkdsk/chkntfs Dirty bit

Every time I boot to win2k (sp1) its set the dirty bit on the boot (c:) ntfs file system. You can run chkdsk during boot, or schedule it during the next boot, but as soon as win2k boots you can:
C:\>chkntfs c:
The type of the file system is NTFS.
C: is dirty. You may use the /C option to schedule chkdsk for
this drive.

Any ideas on whats up with this ? The disk is not reporting and physical/logical problems.