might try something like USB OTG Helper (root required)
the OTG part is sort of a red herring - the purpose of it was initially to allow phones that support OTG at system level, but don't give any UI for actually mounting/unmounting stuff, to be able to.
but what it (and other similar software) basically does, is give a UI that sees removable storage and lets you mount/unmount it. my phone supports ntfs, exfat, ext* - at system level, but there is no UI - but this helper app lets me mount all of those (also supports multiple partitions, yay)
one of the problems is that the Edge, as helf
and others have mentioned, doesn't like it when you put in a microSD or USB flash that is anything other than FAT 16/32. does the Edge support ext*? certainly! but vold.fstab (I think this is where it is set) tells the PE to only allow FAT partitions on microSD/USB.
also: I doubt that the Edge has exfat support since it's a bit old for that, but it would be quite possible to compile a .ko module on the same kernel version, with an ARM toolchain. it would also be a HUGE
headache to set up an environment to only do just that, but not impossible ;-) and even once the module is loaded, still would require a helper app to do the mount/unmount (or mess around with vold.fstab or whatever)