It's totally possible to replace the bad motherboard of a Pavillion 6280T, reinstall a fresh copy of windows and have a pretty stout PC, no? Without all that crap that comes with preloaded Windows from HP?
I'm sure you could do it if you had a replacement HP mobo and a windows CD with the product key. I think I read somewhere that OEMs are not ATX complaint and the I/O slots might not line up.
most oem boards are atx compliant, just find a coppy of windows and not just a reinstall cd. The new board should have any drivers you will need or you can download them.