Compared to the i3, the the other CPU you mentioned (T4400 I think) doesn't compare, as the i3 is definitely superior. I think that you were having issues with the one you tried due to the Intel graphics chip that was in it. Intel graphics chips are junk compared to basically any dedicated gpu out there.
Intel Pentium Dual Core T4400 2.1 GHz,
2 GB DDR3,
and NVIDIA Geforce 310M
Intel i3 330M
2 GB DDR3
Intel HD Graphics
which 1 should i buy??
and my other question, will da T4400 be able 2 run full hd 1080p movies??
Are you open to other suggestions? and if so, do you have a budget? You mentioned in your first post that you wanted to play games. The honest answer is that neither of those systems will do gaming overly well. But as it stands, the GeForce 310M is going to be better than the Intel HD.