Visual Studio extremely slow

I had problem with one application that was extremely slow, when working in Visual Studio (2008).
It was in such a state that I had to upgrade my hardware (new much faster PC) to be able to work at all. And even in this new environment it was painfully slow. While working in all other applications worked very smoothly.

At last I found the reason:
The application have two projects that contains the "business logic".
In both projects there was references set up to several COM-components (used to communicate with a mainframe system). Where in one of those projects these components never had been used.

In a major change in the application most of these COM-components was replaced by another solution, and they was removed from the system.
But: the references was only removed from the project where they had been used. In the other project, where they never had been used, they where not removed.

And it was due to this that the performence when working in VS2008 was a disaster. After removing the references it worked ok.