|What make and model is your brand name system, or what make and model is the mboard?|
Laptop or desktop?
AC Power related events - power spikes, surges, lightning strikes on the power grid - are well known to be likely to damage the computer power supply on a desktop computer - in most cases they don't harm the mboard or the components on it, if the power supply hasn't failed completely.
Failing power supplies are common and can cause your symptoms.
Check your PS.
See response 4 in this:
For a desktop or laptop...
Less likely, an AC power related event may damage the data on the hard driive, or the hard drive itself.
Check your hard drive with the manufacturer's diagnostics.
See the latter part of response 1 in this:
(thanks to Dan Penny for this link:)
Hard Drive Diagnostics Tools and Utilities
If you don't have a floppy drive, you can get a CD image diagnostic utility from most hard drive manufacturer's web sites, but obviously you would need to make a burned CD, preferably a CD-R for best compatibilty, on another computer if you need to.
If the hard drive itself tests okay, any data problems found can be fixed, one way or another.