Windows 2000 NTLDR & Virus

Day 1: Win 2k Pro machine fails to boot because ntdetect.com is missing.

Day 2: 3 computers fail to boot at separate times (including computer from day 1) because ntldr is missing. Run virus scan on all machines on network (even ones withoutproblems) and all come up clean. Reformatted and reinstalled Win 2K pro on machines with problem.

Day 3: Yet another computer (that had not had problems in the previous days) fails to boot because of missing ntldr.

Sounds like a virus, but it isn’t being detected by norton.

any thoughts or suggestions. this is only happening to win 2k machines. company officers are threatening to knock everyone back down to win 98 which would be more trouble than its worth.