I can customize an HP Vista w/ LCD monitor for less than I can buy a CPU only with Windows XP. Why is that?

Answer 1

It depends on the models you are looking at.
Also, companies like HP are often in a better position to have incredible deals than the smaller manufacturer.

Market share is very important to them & like the big car manufacturers they will often include great bundles or rebates to increase shareholder value.

regards,
Philip T