"Ambiguous unit found"

[99Percent]

While rebuilding Lazarus IDE while trying to reinstall a package I get: "Ambiguous unit found" Warning

The unit xxx exists twice in the unit path of the IDE.

I hate to sound like a complete newbie (again) but I am at my wits end trying to figure out how the "unit paths of the IDE" are configured or edited.

Please help.

[Troodon]

If you try installing another package, do you get the same error message?

[99Percent]

For some obscure reason the third party packages got eliminated from the component palette. So I tried to reinstall them but from another directory and that is why I got the message. I proceded to delete the original directory and then I was able to reinstall. But still, I would like to know how the "unit paths of the IDE" are configured or checked.