You're right. I have 3gb.
How are we supposed to know the game requires so much memory?
Usually the listed system requirements for the game work well enough.
However in this case they said 2GB was the minimum amount and the recommended amount was 3GB -- and you have 3GB.
Perhaps a bug is causing a memory leak.
https://en.wikipedia.org/wiki/Memory_leakIs there any way to find out before we buy a game?
I guess you'd have to find someone with similar specs as your computer who's played the game.
If the developers are wrong about the requirements, there's not much you can do.
How old is your computer?
If you have 64-bit Windows 7, would you be able to add memory to the computer or does it already have as much as the motherboard can use?
You might also check what version of video drivers you have, and whether there are better ones for this game.