The cheapest Vista is the copy that comes with a new PC because you get in on the reseller's steep discount.

3. Vista wants a new PC

To get full value from Vista, you're probably going to want to buy a . Many of the benefits of Vista require hardware your current PC doesn't have. "ReadyBoost" and "ReadyDrive," for example, require special hybrid or flash drives. Aero looks awesome, but only if your graphics card supports Pixel Shader 2.0. You can record high-definition cable TV, but only with a tuner card designed to take advantage of that Vista feature. You can enjoy DirectX 10 games, but only with a compatible video card.

Vista's new indexed searching is great, but you'll need extra hard disk space for the index -- and extra storage for the operating system itself. Don't even think about running Vista on a system with less than 1GB of RAM; 2 GB is reasonable and 4GB is the sweet spot. And if you want to really enjoy the , you'll want a 20-inch or larger flat-panel LCD display.

Sure, you can buy Vista and install it on an old PC. But that's like subscribing to HD cable, but not buying an HD TV. You're paying for the HD experience but not actually experiencing it.