Q: I'm right-clicking a virtual machine (VM) in System Center Virtual Machine Manager (SCVMM) but the option Install Virtual Guest Services is grayed out, that is, it's not available--why?
A. In my experience, if the option to install isn't available or is grayed out, this is caused by the OS of the VM being set incorrectly, such as to Unknown. Set the OS to the correct OS you're using, and the Install Virtual Guest Services option should be available.
See John Savill's author page for more FAQs.