It's a simple matter of memory and CPU power. If you have a system with 1 GB of Ram, count Windows to swallow the first 300 to 400 MB, then startup SH3 with GWX and maybe some more mods and you'll fill your Ram as it is. Everything above that will have to be swapped to the pagefile, and believe you don't want an additional 200 MB just for the eye candy.
