Redownload beta 29 if you can't run it on Windows XP. There was also a second update done to fix filenames starting with 16 "F"s if the Pokemon has no PID. (This wrote the Pokemon data wrong in the file as well.)
3.0.0b29
ADDED: Dragging/dropping is now possible from PokeGen to folders to create .pkm files. In addition, it's also possible between instances of PokeGen.
FIXED: Tooltips wouldn't display if balloon-style tooltips are disabled. (Found by "sdfghjklkjhgfds sdfghjiuy" ...)
FIXED: A rounding issue was causing stats to occasionally be off by 1 point. (This only affects the stats displayed in PokeGen and the stats given to party Pokémon. Depositing into the PC or generating a Pokémon for the PC causes all stats to be recalculated by the game to the proper values.) (Found by Anveena.)
FIXED: The update system wasn't processing the download data properly in certain cases. This could cause updates to not be recognized or not be downloaded. (Found by Dark_by_design.)
FIXED: Loading a save file from the command line or by dragging the file onto the executable would cause the list of box numbers on the main dialog to not have a selection. This was causing issues with viewing/setting data, and possibly other things.
FIXED: Dragging a Pokémon from the party to a box slot where a Pokémon already existed would cause the box Pokémon to disappear. (Found by LazurWulf.)
FIXED: In rare cases, dragging non-file objects onto PokeGen could cause errors.
FIXED: There was a minor memory leak related to Pokémon icons.