You can probably play it on Low, although some of the expansion packs have a higher requirement.
You would be better off putting $150 into a used Core 2 Duo system with a 2.6gig if higher CPU and a low end gaming video card like a Radeon 6570, or even a used gaming card. For a used video card you'd want to check to make sure it runs before you buy it. You may be able to find a system that will run WOW pretty well for close to $100.