Generally, it should never be a problem. But if you are actually running high resolutions, basically anything as high as 1920 * 1080 , or multi- monitors, having a stronger card with sufficient dedic. ram, and SPs, pipelines, etc, would be good. This comes in handy especially when running in high player servers. Could be a CPU thing, but when it comes to something like 12 - 13 players, I drop to maybe a 20 - 30 frames. If you plan to run stuff like, F@H, or torrenting, or playing music, you'd better have a bit more than posted.
Other thing, if you are running Vista, don't expect to pull it off with something like a 4200Ti, or what not. I doubt it really. Current IGP or low - end GPUs should always be able to pull it off. Even an EEE PC should do the trick; but then agian, you are running at like 800 x 480 or 1024 x 600.
Never a problem with current computers though, and if anything, you can lower detail, or resolution. It becomes a problem with games using current - day shaders, such as FSX, if you are into flight sims. In such, you may need something like a current or last gen king to do the job.
Graphic cards come in cheap nowadays anyways. I remember when I first built my PC which was only 3 - 4 years ago, where a mid - end GPU like a 6600GT would cost like $200 where, nowadays, an mid - high to even the near top models cost that much. I can buy myself a 4850 for merely $100!
