I'm just glad someone finds the stuff I crammed in my brain usefull.
Some systems are just temperamental, but it might be a sign that it's on it's way out. I can't tell you how often simply stripping a system, cleaning and putting it back together fixed a seemingly fatal problem, but usually it just resurfaces in a new form a few months down the road.
In the end, the industry is moving on; new sockets for CPUs, AGP becomes PCI-express, DDR changes into DDR2 and moves on to DDR3 before you had a chance to catch up. Buying "old" tech becomes prohibitively expensive at some point; I remember spending €90,- on 1GB of PC-133 SDRAM some 2 years ago, not too long before I bought my current system and purchased 2GB of DDR2 for "only" €65,-. Likewise, I payed €90,- for an AGP HD2600, while a little more could get me a PCI-E 8800GT... same price at the time as an AGP 7600GT, iirc.
Anyway, my point is: eventually you're better off spending a lot to catch up than keep spending less at overpriced stuff to keep an outdated box running. (imo of course)