This is a case where spending a little more upfront saves you money in the long run. Cheap hardware fails faster and costs more to replace. Buy quality components from reputable brands and they'll last years longer.

Don't forget about heat. If your computer is shutting down or crashing randomly, open the case and check if the fans are caked with dust. Blow it out with a can of compressed air. Overheating causes a shocking number of 'mystery' problems.

Newegg is your friend for parts. Way cheaper than Best Buy or CompUSA and the customer reviews actually help you avoid junk. Just watch out for shipping on heavy stuff like CRT monitors. Read the reviews before you buy ANYTHING.

I always tell people: buy a UPS battery backup. A $40 one will protect your PC from power surges and brownouts that slowly kill your hardware. Lost a motherboard to a thunderstorm once. Never again.

I build computers for a living and can tell you that most of these problems come down to three things: not enough RAM, outdated drivers, or malware. Check those first before spending money on new hardware.

Honestly at some point a clean reinstall of Windows fixes more than any amount of tinkering. XP gets crufty after a couple years. Back up your files, find your product key, and do a fresh install. It'll feel like a brand new machine.