Problem is most PCs that come with windows, also come with the manufacturers own selection of 'shady programs', trials, adware, etc etc designed to make them some extra money.
Get an Acer. My TravelMate came with no software other than Windows and stuff necessary to operate the hardware (drivers, DVD burner, touchpad enhancements, user guide, etc.) I've needed to reinstall the OS once in its 3-year lifetime.
It helps that I don't install software lightly. I do most of my development in VMWare under a Linux guest OS, and typically run only Winamp/Gaim/Firefox/SSH/uTorrent under Windows. The one time I did need to reinstall the OS was because I'd been going through a bunch of different programs for movie playback/decompression and some of them didn't play very well together.
The same would be true for any other OS that is filled with malicious programs; that is, it's easier to start over than to remove the junk one-by-one.