Depends on what your budget is - APC do cheap UPS models too - and it's got to be cheaper than the cost of a new mobo

!!
The APC Back-UPS ES 350VA will cost around $40, and will give you around 5-10 minutes backup time and has a USB connection to the PC, allowing for automatic file-saving and shutdown as soon as the UPS kicks in. And of course you get the $25k protection plan (although I'm not sure what the catch is...

)
Belkin also does UPS (again, around the $40 mark), similar specs to the APC models.
Have a look at their respective websites (
APC &
Belkin) for more info.
Hope this helps
AndyF