www.pricewatch.com is your best bet for parts unless you have a tax number in which case you can get a decent list of wholesalers from M$'s OEM system builder program...but a tax # is required to purcase from them.

My first tutorial is a bit outdated but may at least point you in the direction you need to get started. I'm working on a followup to address new technologies as well as whats coming down the pipe over the next couple of years. Look for that one in the next few days.