sooo61 That "I/O device error" combined with random disconnections usually means Windows is losing its physical connection to the drive. Since you've already ruled out ports and cables, it's highly likely the USB drive itself is failing internally (either the controller chip is overheating or the flash memory has reached the end of its lifespan).
Before you toss it in the trash, try testing it on another PC just to completely rule out a Windows driver/power issue. If it behaves the same there, here is one last-ditch thing you can try in DiskPart (Note: this will wipe everything, so hopefully you don't have critical data on it):
1. Open DiskPart and type select disk 2.
2. Run clean directly. This completely wipes the partition table instead of jumping straight to creating a new one. (If it gives a write-protect error here, then try running attributes disk clear readonly and clean again).
3. If the clean command actually succeeds without throwing an error, go ahead and try your create partition primary again.
The Verdict:
If DiskPart still throws the I/O error during the clean step, or if the drive drops off while you're doing this, the hardware is dead. Flash drives are cheap to replace, but unfortunately impossible to fix once the internal controller gives up.
