Windows is great for web design...

As far as hosting my websites I stick with Linux. If you have windows XP Professional there is no trouble at all with getting a testing server running on your pc, if you have home or Media Center, its a different story. Also, Vista is so bad, there are rumors of a new operating system coming out from Microsoft January of 2010, and it was ruled the largest OS failure since ME.

I've never seen a machine ever make a difference as far as the design goes. Some designers prefer macs, others windows, but their skills don't get better or worse depending on which machine they are on.