Definitely back up your important files before trying any fixes. I learned this the hard way when I lost 3 years of photos trying to fix a simple problem. Get an external hard drive or burn DVDs of your important stuff first.

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.

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.

Before you do anything drastic, try booting into Safe Mode (tap F8 when the computer starts up). If the problem goes away in Safe Mode it's a software or driver issue, not hardware. That one trick narrows down half of all PC 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.

Make sure you have the latest drivers from the actual manufacturer's website, not whatever Windows Update gives you. Video card drivers especially — nVidia and ATI release new ones every month and they make a real difference.

I build computers for a living and can tell you that most of these problems come down to three things: not enough RAM, outdated drivers, or malware.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.