|Response #1 is quite true and very important whenever installing a new operating system.|
Note though that Windows 7 is NOT a program you can download (not legally), it needs to be purchased and installed. You might not have a legal copy and that can cause all kinds of problems, depending on where you downloaded it from.
If you downloaded a Beta version of Windows 8 from Microsoft, that would be a different story. With the correct drivers installed, it will work fine until about 6 months after the official release date and then begin having periodic restarts if it follows the pattern of the Windows 7 Beta.
Did you make sure that your hardware is supported on Windows 7 and that drivers were available from the manufacturer's site before you installed it?
You have to be a little bit crazy to keep you from going insane.