I can't get Silent Hill 3 to work on Windows 7!?

Okay so recently I downloaded the Silent Hill 3 demo onto my windows 7 laptop to see if it would work. At first it wouldn't run but my friend fixed it by right clicking the shortcut to SH3 on my desktop and going to Properties, then to compatibility and changing the settings to make it run in compatibility mode for windows 98 and checking the boxes for it to run in 256 colors and in 640 x 480 resolution. It worked and I was so pleased I decided to get my hands on the full version. I have it now but it won't run even though I followed the steps my friend took to make the demo run. My screen just goes black, then all magnified and strange colored and then black again and back to my normal desktop. Any suggestions on how to make it work? Any help is greatly appreciated as I've wanted to play this game for ages now!