Here is a post with some procedures to try.
And this is from the MioPocket Readme.txt
My Mio Moov won't boot or connect to USB!
If this has happened to you (usually because you renamed AppStartupSec.exe or modified paths.xml, both of which you should never do), turn the device off and, while it's off, connect the USB cable (which, on the other end, is connected to your computer), then turn the device on. If a USB connection is not established, repeat this many, many times by turning the device off and back on; eventually, it may connect. If it connects, undo the file & folder changes that you did to the flash drive.
[color="red"]This is what i was going to suggest but it needs a SD card[/color]
Another thing to try is to get an SD card and create a "Cobia" folder on it that corresponds to section 2.2a4B (SD installation instructions for Moovs). Next, copy MioAutoRun\Programs\FileManCE2\FileManCE.exe to that folder and rename it to Auto.exe. Finally, put the device's power switch in the reset position, then in the on position, and as soon as the "USB connection" screen is shown (if it's shown), insert the SD card. If it works, the FileMan file browser will launch. At that point, undo the file & folder changes that you did to the flash drive.
If both of those tricks don't work, there *may* be a way to establish a USB connection by opening up the Moov and shorting two pins. Poster "al13lea" came up with this. Here is my interpretation of his instructions:
1. Open the Moov's case by removing two little screws.
2. Notice 4 pins near the RESET/OFF/ON switch in which pins 1 & 2 form a pair and, slightly further away, pins 3 & 4 form a pair (ex. "|| ||" or "1 2 3 4").
3. Connect the Moov through the USB cable to your computer.
4. Take a piece of conductive medal (such as a coin) and touch both of (and only) the middle two pins (pins 2 & 3) with it. If nothing happens after a few seconds, try doing the same with the two left-most pins (pins 1 & 2).
5. If successful, you should have the device recognized in Windows. At that point, undo the file & folder changes that you made earlier and which caused the problem.
Good luck!