I had the same thing when I was installing an AGP driver on my mobo, I just had to dl the latest version and all was good.
I'd suggest booting in safe mode, removing all mobo, graphics card, sound card etc drivers, then see if it boots normally. If it does go to all the various manufacturers sites, and dl all the latest versions of all the drivers you need, then install them, starting with the mobo drivers.
Hope that helps...
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