the power supply is 300 watts no name brand, on a Pentium 4 system. Besides the essentials I'm only running a SoundBlaster Audigy off it and a CDRW...the fan's noise keeps getting higher pitched then comes back down...then higher pictched....etc. I'm not even using the CD drive when it happens. Should I worry about this? I don't mind losing the power supply but I don't want it to go out with a bang and my computer to fry with it. It's been doing this for a day now, and it's about 7 months old.

Any help is very appreciated.

I have had a couple of power supplies go bad, usually what you describe happens first, then the fan stops working. One ithink i remember replaceing when the fan stopped and another i just let cook in its own heat until the computer wouldnt boot anymore :)
Ive never seen one go out with a bang :) if the fan stops working replace it.
A power supply can last months after it starts getting loud though.