I found problem in Windows 2000 professional and then I re-installed in different directory C:/winnt1 using WINDOWS 2000 dumped CD in drive D. While startup I find dual boot up options for "Windows 2000 professional". The later installed version working OK but I want to remove older version of Windows 2000 lying idle in c:\winnt. Deleting option in boots.ini may solve problem of dual boot, but earlied version has to be removed to save disk space and for stability ofthe system. When two windows 2000 loaded in same drive C, please help how to remove one from the system. In Drive D ,I keep personal data and D is not operating system. One advised me to format it. If so, tell me the procedure to format C drive NTFS using bootable floppy.

just delete the winnt folder which is the older one and leave the new as it is

Make sure you modify the boot.ini BEFORE you reboot after deleting the other Windows 2000 directory.
I made this mistake and it would not boot.
I eventually had to use the start up discs to get to a prompt so I could edit the boot.ini so it was not looking for the directory I just deleted.