BUT displayed bulk list of errors that "ERROR constraint relation already exists.............etc" repeating many lines
Is any problem with foreign key constraint.
That means that the tables (and all their constraints) already exist in the target database.
You need to drop them first if you want to run the dump script.
That's one of the reasons I prefer the custom format over the SQL script dump: you can decide when you import it if you also want to drop everything that is contained in the the dump.
With the SQL dump you need to include the --clean option when generating the dump to make that happen.
As you already have the SQL dump, the only thing you can do is to drop everything from the target database.
And again: please do not store user data in "c:\Program Files". That directory is protected for a good reason. If you can store files in there it either means you are working as an administrator (which you shouldn't do) or you opened up the privileges on the directory (which you shouldn't do either).