Yeah, basically to combine the above two posts,
The IGP Northbridge has an inegrated video set based on the GeFrorce MX. Because it has to use system memory instead of its own dedicated ram, you'll have more issues with speed and overclockability. Dedicated video ram on any decent card is faster than regualr ram. Also, you'll want at least 2 X 256Mb of ram preferably PC2700 or above.
With the SPP you lose the integrated video which means you can buy any AGP 3.0 based card you want. This allows you to have the best gaming performance and because the system ram is used solely by the cpu, you have more stable overclocks.
Basically, if you want to save some money and don't need hardcore gaming, then the IGP will work fine. I'd use it for a net box for my grandmom or something. Or possibly in some sort of router solution.