It would appear that there's something wrong with the Windows version of 6.3.5 because PNG is not listed as a supported type by my system either.
It would probably explain the problems with PNG that I mentioned in another recent topic:
viewtopic.php?f=1&t=9363
Pete
Windows XP and PNG support?
Re: Windows XP and PNG support?
We will update the Windows binaries sometime tomorrow with proper PNG support.