The uninstaller never works after you have patched Trainz, the dat file isn't actually corrupt, without getting horribly technical, it contains the details of the original files installed, as they are different after patching it can't find them and the uninstaller has just bombed out with a generic dat file corrupt message.
As Shane said use Revo uninstaller.
Incidentally unless you have a space problem there is no need to uninstall other versions of Trainz, they will happily co-exist.
If you are thinking of a screenshot for the error message, don't bother, not needed, it's a well known annoyance of N3V's bad uninstaller setup.
Screenshots folder in 2009 is in your TS2009 folder.