gta4 is like the worst port ever, even a quad with a good gpu struggles. and with tour 640m which is slower than 640 of a desktop, you probably can but it will not be that good. lower the settings maybe
Not with those specs it is not, at least not a traditional, upgradeable dekstop. The "M" on the end of the CPU and GPU models denote "Mobile".
The only time I can think that a "desktop" would have that CPU and GPU is if its one of those new super slim things designed to be used as an HTPC.
It's an all in one desktop that's why, so basically i can run it decently right like medium settings and expect 19-25fps?
At 1080p? You would be lucky to get that on LOW I think. My laptops GPU is not a whole lot less poweful than that 640m I think and I struggle at 1280x720 on low/medium, however your CPU is FAR more powerful than mine. AIO PCs are NOT meant for gaming AT ALL.
Single player will probably be playable, but it will kick you out of multiplayer after a few minutes for low performance.