I have a similar problem. I'm trying to replace a Compaq Spare system Board 845 (280318-001) with a new motherboard and processor. How can I know if this is a Micro or Baby, so the new motherboard would fit in the same case that I have already? Thanks!

Conpaqs sometimes have a specially designed case that is unconventional in design so if you are getting a new motherboard and processor I recommend that you just build a new computer. You will quite possibly have to get a more powerful power supply to handle the motherboard as well as new ram to avoid a mismatch. This is especially true if you have an older computer. Knowing the model number might help in figuring out the case type and whether or not it would be appropriate to continue using that case and the other parts. Also you will have to procure your own copy of windows because a copy of windows from a compaq will only work on a compaq. This is more involved than simply buying a new motherboard and processor.