Looking for a 3D rendering program

[Mellowyellow]

Like title says I am looking for one that is free and will work with Windows 7. If you know of any, post up please thanks!!!
Looking to design a computer case.

[lalPOOO]

Checkout sketchup. There may also be a personal learning edition of maya available which usually comes with a ton of tutorials and forum support. I have no experience with sketchup, but I did learn the basics of maya a few years back and if you're willing to invest the time into learning it is an extremely powerful program.