I just replaced a Dell Dimension 8400 motherboard with an identical board (new) not purchased from Dell. My thought was hopefully I would not have to reload the OS, etc. The first 3-4 times I booted I got the BOD which was discouraging. However, I removed the CMOS battery for a few seconds, replaced it and the computer then booted into Safe Mode and the on the next boot, it booted normally.
Everything from this point on is normal and I did not lose a thing.

I did observe, however, when looking at the CMOS, there was no Express Service Code or Service Tag Number. I guess that is to be expected and is no big deal.

My question is: If I would have had to reload with WXP Pro using a valid Dell WXP Pro CD, would it have worked? I suspect the original Product ID was held somewhere on the MOBO and the CD would have looked for it and would not have found it. Is that correct???

Just curious. If it didn't work, would Microsoft have provided a valid code free??