Question : Multiple MSDE Databases on one server

I have a customer with an economy application that runs on MSDE Database.

Now, they have bought Veritas Backup Exec 10, which also runs on MSDE database.

how can I have both these databases work on the same server.

Answer : Multiple MSDE Databases on one server

The install program from your vendor is probably trying to install a default instance.  Does it give you an option to use an existing instance?  If so, you can download MSDE, install a new instance and point the application to it