Ela,
I assume you're referring to a no-longer valid Enterprise project template.
If so, perform the following steps:
1. Open PWA
2. Select Admin / Clean up Project Server database
3. Select the Projects and To-Do lists radio button to active the grid with
all projects
4. In the Type column filter for templates only
5. Mark the template you want to delete
6. in the bottom right corner of the site click the delete button
Hope this helps...
Marc