Greenshot\unis000.dat does not exist
Even after reinstalling can't uninstall
That's strange, also the first time someone reports this. But you did use the exe installer, right? (As opposed to the ZIP or PortableApps release)
We are using InnoSetup for the installer, normally it takes care of creating unins000.dat. And even if it gets lost somehow, re-installing should create it again. So I am not sure what has happened there...
Did the re-install actually go into the same folder as your previous installation?
InnoSetup has logging capabilities (see InnoSetup page), so if you run the installer like
we might find some more helpful information in the log file InnoSetup creates.
If all goes wrong, you might want to remove it manually - the installer just creates a single registry entry (see here).
Please let us know whether you need more assistance with this.
Thanks and best regards,
If the information that Jens gave you doesn't help, please also let us know what version you installed.