Microsoft has written an article listing the hardware specifications you will most likely need for Windows Vista to run efficiently.

CPU
Minimum: mid-range 32bit CPU.
Recommended: 64bit CPU.

Memory
Minimum: 512MB RAM.
Recommended: 1GB RAM.

Graphics
Minimum: GPU that supports DirectX 9 and has at least 64 MB of graphics memory.
If you are building a new PC, make sure you get a motherboard that has a seperate AGP or PCI-E slot.

Hard-Drives
Minimum: IDE hard disk with a speed of 7200 RPM and a 2 MB cache.
Recommended: SATA drive with an 8 MB cache and Native Command Queuing (NCQ).

Optical Drives
Minimum: A DVD drive.
Recommended: DVD±RW.

Networking
Laptop: Built-in 802.11 wireless capability.
Home PC: At least 100 Mb of Ethernet capability.

So overall, Windows Vista won’t need the absolute top-end products to be fully functional, mid-range products will do fine.

Microsoft has recently updated their Genuine Windows Validation tool to stop one workaround for it. Users now have to copy a generated code and paste it into a form before they can actually get to the thing they wanted to do. The workaround was a simple thing that could be done just by pasting a snippet of JavaScript code into the address bar.

This update only fixes one of the many still available ways of getting around this protection scheme. I think what Microsoft has done is made it more hard and time-consuming for users who have legal copies of Windows, because people with a illegal version can simply find another method.