I'm running Windows 7. I've tried practically everything.
I assume you tried sticking it back into the exact same USB port you removed it from? If not, I would try to see if it shows up there (in this situation don't expect an OS message - just check you drive list to see if the USB is there. If it is stop it in windows and then remove it.
If it's a fact that it doesn't work in any other PC - the possibility exists that the reason you saw low to know transfer rate is that it finnally failed/died; and if that's the case, reformatting won't help.