No problem. Hit escape, selsct "options", under "video" you should be able to select the resolution. Or "full screen" should (try to?) fit the game to your screen size. What is the resolution you are using?
minute or three to start, eh? It does sound very painful.
1. Is there other stuff running? Maybe hiding in the background and munching on system resources?
2. Is the hard drive running the whole time? I.e. is the system swapping?
3. What sort of hardware do you have - CPU, RAM, OS?