When I first built my computer about a year ago:

300 Watt Power Supply
1.67GHz AMD Athlon XP 2000+
512MB DDR RAM
128MB GeForce4 Ti4200
Gigabtye GA-7VRX Motherboard w/ VIA KT333 Chipset
3 1/2 Floppy Drive
2 Western Digital 7200 RPM Hard Drives
2 CD ROM drives - (Liteon 52x CD-ROM / Samsung SM-316 - 16x CD-R - 10x CD-RW - 40x CD-ROM - 12x DVD-ROM)
SoundBlaster Audigy Gamer
RealTek NIC
2 Expanded USB 2.0 Ports
1 Game Port Extension From Sound Card

My fps was steady at around 100 on most occasions, peaking to its capped 125.  The lowest it ever got was around 70 fps, except for the demolition bomb.  Over the past year, it has dropped to a max fps of 60, dropping down to 20 at times.  Over the time, I have expanded:

3 case fans (1 in, 2 out)
1GB (512MB added) DDR RAM
Overclock to 1750 MHz (133 MHz FSB to 140 MHz)

On occasion, I hear a beeping noise from my computer, but it only happens once very briefly, and goes away for awhile.  It's not an overheating problem, my temperatures are fine.  My first problem was my graphics card fan going bad, I sent it in and they couldn't find anything wrong, I eventually just ordered a new fan.  It worked... but only temporarily.  I have had one or 2 other problems, such as one of my cd drives not recognizing some cds properly (the burner/dvd).  The only thing that I can think of would be the power supply isn't sufficient for all that I have in there... should I upgrade that or would the problem lie elsewhere?

Peripherals that get their power from the computer:

Logitech Optical WheelMouse
Logitech QuickCam Pro 4000 (added later on)
Logitech WingMan Attack 2 (Joystick)
IBM Rapid Access Keyboard

Other peripherals:

IBM E74 Monitor
Logitech z680 Speaker System - 500 Watts
HP DeskJet 682C (yes, it's old)
HP ScanJet 5100C (yes, that's old too)

the occasional beep may from your keyboard.  

that CPU doesn't eally like to be overclocked in my experience, well, i should say, it doestn' like to be overclocked MUCH.  i managed 1.85 or something on a 166fsb (unlocked it).

when was the last time you completely backed up everything and started over?  i did that a couple of weeks ago, and saw my fps go up significantly.  RMG's are now almost always over 80.  try a defrag?

Auto-defrag every day, and the beep is many times while I am away from my computer, it is from the internal speaker, but I hear it as I am near my computer.

As for a reformat, I have not tried in awhile, but I don't think it's necessary as every other non-graphic intensive usage is fine, I have run registry checks and spyware elimination tools, as well as an AntiVirus with up to date definitions and Windows XP Updates.

Not to mention, this CD Drive problem has been from the beginning, and I'm wondering if it is just as I add more peripherals that it juices my power supply even more past it's limit...  considering my power supply is only 300 watts.

the PS would be my guess, though i would format/reinstall first, see if that does anything to improve it (could save you some $$).   I have noticed significant boost in FPS after a format/install...  If not, upgrade that PS, youll need to eventually anyways, right?

a good 300 is way better than a bad 400.  i bet ur PSU is fine, unless your getting random rebotos and such.  "slowness"  or "fps drops"  cannot be attributed to a psu.

serious, i know reformatting is a pain in the ass, but the benifits ARE real.

The thing is, I do a bit of programming, and I can't get back most of the stuff that I have on my computer, due to certain unmentionable reasons (i.e. Microsoft Visual Studio, Dreamweaver, Photoshop).  I could see if I could find a backup, but there is so much on my computer that it would take me forever to get back.  I would like to only use that as a last resort, as I'm sure everything is clean and defragged, no windows errors.  I'll check into the power supply, because the beeping is being caused by something, and it's not the heat nor the keyboard.  I'd rather spend an entire day cleaning my system out than an entire day reformatting and attempting to get my settings and everything else back.

The beep is being caused by your bios, i read the thread somewhere if i  find it it is very helpfull ..  
certain number of  beeps for a  certain problem ,,,,  if i turn it up ill post the thread

Is the beeping when you press 3 buttons at the same time?

I heard that's an issue with some keyboards. Mine does it quite often