The 6100 will technically run C&C Generals, but not very well. It's only onboard video, after all. I think the max shared RAM for it is 128MB, but it could be 192MB for the 6150/LE chipset. I'm not certain on that.
The onboard video chipsets are indeed cheap, but they cut a few too many corners to be considered ideal for a gaming system. I understand that price is a concern, but just be careful about the mobo you pick out. Don't skimp too much!