I am not saying that you HAVE bad caps, I'm only suggesting that it makes sense to start investigating hardware first. I have had several machines with bad caps load BIOS, install OS, pass memtest, etc. (i wouldn't recommend flashing a BIOS with bad caps - greater odds of 'bricking').
Relating to my earlier post, if you have a cap rated at 2000 hours at 85°C, in a thermal zone that averages 75°C, the average life expectancy of that part will only be 4000 hours. That only adds up to about 167 days of continuous use (at 75°C)!
Read the full post first, especially the part about known symptoms (even add-in controllers can be affected). I especially notices the guy with 60 GX's, that had 40 of them fail.
Failures generally start with (insufficient cooling) the power supply. It is difficult to see inside them. If you want to examine it, ensure that you PULL THE AC cord out, first! Hold down the power button for at least 15 seconds , to ensure ALL power has been drained from the P/S. Remove it, open the lid, blow it out with compressed air (clean the mobo while your at it - just don't make direct contact between the nozzle & parts) & then visually inspect. Ensure that the p/s is fully re-assembled before trying it under AC (the innards can KILL - even if you don't directly touch)
If you are not comfortable opening it up, perhaps try a known good p/s (even though it will likely not look nice).
IF you determine that this is a source of error in your machine, & your not comfortable working with a soldering iron (or safety with AC), i would humbly say that maybe it is time to investigate a replacement. (& the cost-effectiveness) Remember, caps can 'fail' (dry out), even without showing outward signs. If you have had this problem for a while, at least one should be obvious. Non-contact infrared thermometers are relatively inexpensive, & invaluable when identifying thermal-zones.
I am sure that you know how Windows XP is notoriously bad at moving onto a set of hardware that is different from the hardware that it was originally installed on
No, actually i don't know how xp is notorious at different hw, i always use the 'Standard PCI IDE Controller' driver when migrating to different hardware. I suppose that doesn't apply if you are using a 'Restore' disc. Isn't there a '32 bit Diagnostic' CD (or the like) available for your hardware?
Maybe i'm wrong, i still have much to learn, even after 30 years working around 'puters! I have learned new ideas from even the youngest & oldest of 'nubes'.
Forgive me if i have been short of patience, or rude, my Canucks are playing now. 
