MSHTML in Silverlight

Question

I am trying to use MSHTML in a Silverlight application. I created a Silverlight application and added a WebBrowser control to the MainPage.xaml. In the designer the WebBrowser control says that HTML is enabled only in OOB mode so I enabled OOB mode.

When I try to add a reference to mshtml.tlb I get the error message "An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B)". I am able to add a reference to mshtml.tlb for other applications. When I research that error, it seems there is an inconsistency between 32-bit and 64-bit.

It is confusing. If someone knows what I am doing wrong then that could save me tme. Otherwise I will continue to attempt to figure it out.