Windows XP
    Start>Run>chkntfs /x <drive> [drive] [drive]
    For example, if you want to disable Chkdsk from running on drive C: chkntfs /x c:
    Chkntfs works by modifying the BootExecute value in the Registry.
    HKEY_LOCAL_MACHINE\SYSTEM\CURRENTCONTROLSET\CONTROL\Session Manager
    The default value is BootExecute:REG_MULTI_SZ:autocheck autochk *
    Chkdsk /f /r is unaffected by chkntfs and can be run to check volumes manually on the next system reboot.
This from: 
http://www.marvswindowstips.com/on_off.htm
Looks solid to me.