This drive appears to be OK when I put it in an enclosure and stick it in my other PC, but it won't boot. It was the master HDD in another PC and I need it to boot so I can use a very expensive program on it. Can I do something? I think the OS was W2000.
Rob

We need more information!

When it's supposed to boot, what error message do you get? Do you ever see it start to boot Windows?

If you keep tapping the F8 key, can you get into the advanced options menu?

Did you do something right before it stopped booting? Anything else to tell?

Hy!

If your enclosure is an USB case: Older motherboards cant boot from USB, so check it, can the new PC boot from it (you can find this option in the PC's BIOS).
If the two PC are from different components (CPU, RAM, etc), the OS can hang, and stops at boot, or reset the PC.
Check the drive in the first PC, can boot the drive in them.