I don't know about you, but whenever I go to Dell's, HP's, or any other major PC manufacturer's Web site to look at new computers, I get a little overwhelmed with all the decisions I have to make. Do I want a home office or a small business computer? Media center capabilities or a machine that's all business? And those are the easy questions--after that come the big decisions: CPU and memory.What's the difference between AMD's Athlon 64 X2 4200+ and its Athlon 64 X2 5000+? How much faster is Intel's Pentium D 960 than its Pentium D 920? Why is Core 2 Duo better than Core Duo? Of course, these questions are compounded if you're building your own system from scratch--then you can choose any processor you want, not just the options the PC makers spoon-feed you.

That's where our "Dual-Core CPU Buyer's Guide" comes in. We provide detailed information about the technological advances made by AMD and Intel in the past year and how those advances translate to their current processor lineups. We hail today's top chip, but also point you to more affordable options that still provide outstanding speed and efficiency.

There's also the question of cost. If I choose the Athlon 64 X2 5000+ over the 4200+ for an HP Pavilion m7660e, the manufacturer's online store adds $140 to my price. Is that fair? Is HP just passing along the cost of the higher-end processor, or is the company padding the cost a bit? Our buyer's guide can help here as well. A glance at the quick-reference charts shows that individuals can expect to find the 5000+ for around $325 and the 4200+ for around $199, a difference of $126. Although HP pays significantly lower prices because it buys in bulk, the price difference between the two chips is more or less comparable. (Keep in mind, too, that chip prices fluctuate frequently.) So perhaps HP is padding a little, but not a huge amount.

Our guide also provides pointers to some bargains you might otherwise overlook, such as the dual-core Pentium D 800 series and the low-end single-core Celeron and Sempron series. It also steers you away from overpriced chips such as the single-core Pentium 4s.

Now what about memory? Is more always better? Well, yes and no. In "Analysis: How Much System Memory Is Really Enough?" our tester found that adding more memory usually helps, but using memory modules in dual-channel mode is the real key to improving performance. If given the option, always choose the dual-channel configuration.

So there you have it: help for two of the biggest headache-inducing PC-buying decisions. Two down, a million to go. What decisions stump you when buying a new computer? Graphics card, additional software, extended service plan? Share your advice on these and other PC-buying decisions below.