When developing Visual Studio extensions, they’re deployed to experimental instance, and can be annoying if you don’t want them anymore.
You can either uninstall them via Extension Manager, or reset the experimental instance using CreateExpInstance command.
For me (I’m running VS2010 SP1) the complete command is
"C:Program Files (x86)Microsoft Visual Studio 2010 SDK SP1VisualStudioIntegrationToolsBinCreateExpInstance.exe" /Reset /VSInstance=10.0 /RootSuffix=Exp