I have yet to find any PC that didn't hang up. As such I can write that a no hang PC has yet to be made.
As to the 3GB RAM, that's a sign this is a value machine. The 5470 GPU is at the low end and should be an OK solution unless you have a GAMER in the house. As to 512MB video graphics the GAME will tell you if that's enough.
Your comment about Windows 7 takes up a lot of memory is a strange one. I found it takes less than Vista!
I am planning to buy Sony VAIO VPCEB34EN - i3-370, 3gb RAM, 512 Mb ATI graphics card,Win 7...I want to know if I wud be able to play games like Microsoft Flight Sim, Call of Duty etc. without any hang-ups on this laptop, considering Win 7 takes up a lot of memory...so wud 512 Mb of graphics card be sufficient??