|The flash drive (or external drive, or memory card reader) must be plugged into a port it will actually work in.|
The flash drive MAY NOT show up in My Computer or Windows Explorer if it's data is damaged. It sounds like the flash drive is being recognized as a hardware device, but the data on it is not being recognized.
How to tell if the flash drive is properly recognized as a hardware device, even if you can't access it's data.
Programs you can try to recover your data, if that's okay.
The most frequent reason people can no longer access the data on a USB flash drive, USB External drive, or a memory card
See Response 2:
Go to Device Manager.
e.g. RIGHT click on My Computer - Properties - Hardware - Device Manager
If the USB controllers entry is there but it's NOT opened up to reveal what's in it, there's nothing wrong with the USB controllers or the drivers for them.
If the USB controllers entry is there and it IS opened up to reveal what's in it, tell us which entry(ies) has(have) a red X or yellow ! beside it(them).
If the USB controllers entry is NOT there, then either you USB controllers are not enabled in the mboards bios Setup, or they are not working for some other hardware related reason (e.g. your power supply is no longer producing 5v, or, extremely unlikely, the USB controllers are fried).
NOTE that some laptops have no entry that enables/disables USB controllers - in that case they are always enabled.