I had very similar issues with Incredibuild & ViEmu.
I'm using Visual Studio 7.1 and Incredibuild was already installed and when I installed ViEmu all the Incredibuild stuff disappeared.
Again, like the previous poster, un & reinstalling seems to have gotten everything together.
Here's the sequence as far as I could tell:
VS 7.1
Install Incredibuild
+ Incredibuild Ok!
Install ViEmu
+ ViEmu Ok - Incredibuild Gone
Reinstall Incredibuild
+ ViEmu Ok - Incredibuild Gone
Uninstall ViEmu
+ ViEmu Gone - Incredibuild Ok
Reinstall ViEmu
+ ViEmu Ok - Incredibuild Ok
Perhaps ViEmu is using some old path to install itself. Looks like at least with VS 7.1 the way to register an add-in is documented. I use Incredibuild and Workspace Whiz and they both show up in Tools->Add In-Manager dialog box. ViEmu doesn't.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vsintro7/html/vxconAdd-InRegistration.asp