VS 2008 Using SQL compact server in VB.NET

Hello,

I know this may be a DB question but it is related to VS2008 because of how it acts.

I created a table and tried saving it. Gave me an error which I forget. Restarted VS and reloaded the VB.NET project. It is there but with an extension SFD1 instead of SFD. How did this happen? Anything I can do to fix it?

Thanks!!