If you value the data on the hard drive and have access to another PC I would immediately connect your hard drive as a slave drive in another PC and image or copy it before turning the machine on again. There is a possibility the PSU or MB was damaged by brown power (less voltage than standard) or there was some surge damage to some of the components, hopefully not the hard drive. If you're all backed up & OK then I would download and run your drive maker's diagnostic tool. It runs in DOS so Windows is not involved. Next check out the PSU, test the output voltage with a multimeter or a $20 PSU tester.
You could also try a repair install (second repair option) of Win2K from the CD, you will lose all your updates but it might get you back up.
There are Smart UPSes (battery + surge protector) with power regulation, correction and conditioning features that cost less than $100. Remember power-strip surge protectors deteriorate over time and 'wear out' to the point they offer no protection. A smart UPS will also safely shut your PC down unattended. I wish you the best.
Tony