I'm sorry for the late reply here, and hope you have this resolved, but hopefully this will help others in a similar predicament:
In replacing a motherboard (after a blue screen or not) you are not simply replacing the holder for the CPU and memory. The modern motherboard has a lot of devices built into it, which may include one or more of
- Video adapter
- Network Adapter
- Sound card
- USB adapter
- PCI adapter
- IDE adapter
- SATA Adapter
- SCSI Adapter
The list goes on and on. The short story is, the computer shut down with a specific list of devices connected, and reboots to find a whole new range of devices attached, but no hint as to what happened!
To put this in human terms, imagine you wake up one morning and find you have eight legs instead of two? Going to be kinda wobbly for a while, right?
In the case of changing out a motherboard, you need to re-run the hardware wizard to let it figure out what is now connected, and what is gone. You may even have to re-run the installation software to get it sorted out - it shouldn't need a full install, just access to the drivers from the installation CD/DVD.
Just a word of warning on this, if your OS came pre-installed, it may be keyed to the hard drive serial number or the CPU serial number, so the re-installation may fail because of this - DAMHIK (Don't ask me how I know)!