What does the error say? Just copy&paste it here or something so that we can see it, otherwise nobody can help you. I don't know about you, but I see dozens of errors every day.

You've got the project open from a read-only location - you should have got a warning about this when you opened the project (if you did, ignoring it was your first mistake :-) ) You can't compile a scenario if it's in a read-only location. Use "save a copy as" (from the "scenario" menu) to save the scenario to a different location (somewhere under your own documents folder) and then open the scenario at that location ("open..." from the scenario menu) before you close the original version.