|Flash drives are always software partitioned and formatted when they are new.|
In your case, it would probably be using FAT32 software partitioning.
You can re-format flash drives in Windows, but Windows itself will not allow you to delete the partition(s) on the drive, so Windows should detect the drive fine in My Computer or Windows Explorer fine, unless .....
- (unlikely) you used some third party program to delete the partition(s) on the drive, or you software partitioned it but did not format it, or you software partitioned and formatted the drive with something Windows can't recognize
- (unlikely) you were formatting the drive and interrupted the formatting before it was complete
- or, (possibly) you have damaged the flash drive, such as by dropping it
-or, a lot more likely,
- you do not have the flash drive plugged into a USB port than it can be recognized properly in,
- OR - you have damaged the data on the drive. If that's what is wrong, the drive is probably being recognized in Disk Management and in Device Manager, it's just not showing up My Computer or Windows Explorer.
Troubleshooting USB device problems including for flash drives, external drives, memory cards.
See Response 1:
If you have not dropped the drive or otherwise damaged it, your problem was probably caused by you NOT clicking on the Safely Remove Hardware icon in your Taskbar and STOPping accessing the drive BEFORE you unplugged the drive while Windows was running.
There are several programs that you could try that will probably fix your problem.
Specifically, links to some programs that can repair the data damage are here -
see response 2: