COSMOS and Visual C# issues...?

Alrighty, so i'm workin with COSMOS. So I have VS2010 and it says that the new version works with that. And its express BTW. So of course it gives me an error. Well, I tried it with 2008 on another pc and got no errors. The problem is, I cannot install 2008 b/c it thinks it's already installed. And its not! It used to be but I un-installed it! :P WTF??? Any ideas? Wehn I try 2 install it, it lets me uninstall or reinstall/repair. Well, if I uninstall it, it still wont lemme install it and if i re-install/repair, it doesnt even do anything. Any ideas?