Comment 1 for bug 621631

The program actually does check what the filesystem of the USB drive is, and if it's ext2/3 then it should indeed install extlinux to it, and if it is neither ext2/3 or FAT16/32 then the drive shouldn't be listed. This might be an issue specific to the distribution you're attempting to install or using.

Are you using the current UNetbootin release binary (the one that ships in various distributions tends to be outdated and may predate the ext3 support)?

Also, was a file called extlinux.conf created in the root directory on the USB drive?

Also, what distribution are you using, and what iso file did you attempt to load? (I tested installation to ext3 only with the Ubuntu 9.10 desktop iso on Ubuntu 9.10)