I need video Card Help?

since you have AGP 8x. mostly its a 128/256bits bus interface. The difference between GDDR1 and DDR. GDDR1 is high speed ram dedicated for Video card, DDR is system ram. Both totally difference, you can use GDDR3 when you have DDR1 and vis-versa And Low profile video card are shorter video card for small computer like the Shuttle.