Yea, your on-board video chipset is keeping you from playing those games.
I would suggest buying a new video card as your motherboard has an available PCI Express slot.
You could get something like the ZOTAC GeForce 8800 GT
for $149.00 that will play all your games with ease.
If you don't mind spending a bit more, the DIAMOND Radeon HD 4850
for $174.99. It's performance can't be beat at that price.