It's always been funny watching Dell's back-and-forth between offering systems without Windows and requiring it. Two years ago, hilarity ensued when Windows become optional on some models, but removing it from the system did not reduce the price of it. They seem to be learning from their ways, however, and recently have started offering several desktop models with no OS at all, with prices to reflect it. While of course that brings along no software warranty with it, that is exactly what many people want.
They're offering some older-gen technology, sadly enough, with these, sporting the Pentium D 820 and the X2 3800+, though the prices reflect this as well. If you're looking for a cheap system with just the hardware and don't want to build it yourself, they're definitely worth looking at.