I'm going to agree with most people here, in saying:
Build it yourself!
It's more fun, gives you more control, usually cheaper and you will get a system that is easier to upgrade. Plus, your windows installation will not be bogged down by 200 pieces of useless software right from the start. I don't think I've ever used any of the software that were pre-installed on my systems anyway. I cannot really see any positive points to purchasing a pre-built system.
Garcian's recommendation is very good, if you want a not so pricey computer.
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