Webmatrix installer acting up

I've set up a VM using Virtualbox, 32-bit Win7 Professional(key via MSDNAA), for hosting & developping some ASP.NET/Silverlight sites.

I ran webm开发者_JAVA技巧atrix, it installed needed dependencies for itself. Then I installed VS2010.

Now, whenever I try to run webmatrix, it tells me it still needs to install itself. When I click "install", the option window that opens up only shows "I Decline". What's going on here?