Every time I build a new PC, some decisions absolutely haunt me. One of these is how much RAM to get, and since it's now a business expense, I tend to overspec how much I'll actually need and then ...

I've got some old RAM lying around that I'm looking to use. What are the rules on mixing RAM? As long as they're the same modules (DDR, DDR2, etc.), should I experience any performance issues? You are ...