Going by the comments on this sitewww.gog.com/forum/general/schizm_dvd_on_windows_7
whether it works properly or not on Windows 7 depends on your video card drivers.
But the fact that yours doesn't install at all (or installs really slowly) makes me think of a few possibilities:
1. The install box is inaccurate in Windows 7 and does not display progress even though it's taking place. It's a long install. Check your hard drive light for activity instead of going by the progress bar.
2. Your disc is damaged/marginal and hard to read. Try copying the contents of both sides of the DVD to a folder on your hard drive to make sure the disc is readable.
3. Change the Setup file on the DVD to run in compatibility mode for Win 98 or 2000 or XP before starting the installation.