The error message says the perl512.dll not found. Not that is there and it can not use it.
I think you'll find that it's pretty much as choroba has said. If your Data/Dumper is from a perl-5.12 installation, then Dumper.dll won't load unless it finds perl512.dll.
If it can't find perl512.dll then you'll get the error message that you posted in the transcript in your first post, and you'll probably also get a pop-up that tells you that perl512.dll could not be found.
Re-installing Data-Dumper might fix the immediate problem, but if there's one module hanging around from a previous perl installation, then there's probably others.
I met exactly the same error recently. It is possible that the reason is different in your case, but this was mine: A new version of Perl was installed, but the previous version of Perl was not uninstalled properly. When Perl was looking for its modules, it sometimes found them in the old Perl directories and tried to use them. Some of them triggered the error.