1. Insert your flash drive into the computer and wait until the readiness (if any) light stops flashing. If a message pops up on the screen asking if you want to format the drive---click 'no.'
2. Left click on the 'Start' button, then left click on 'My Computer' or 'Computer.' You should see the icon for your flash drive listed. If you don't, skip to step 5. Right click on the drive and choose 'Properties.'

3. A window will open up showing the properties of your flash drive. You may also see a pie chart icon indicating its full/empty status. Click on the tab at the top of this window that says 'Tools.'
4. Click the 'Check Now' button under 'Error Checking' to start Windows error checking the drive. You will get a window that pops up asking if you want Windows to fix any errors that are found, check that box as well as the box for 'Scan for and attempt recovery of bad sectors,' then click 'Start.' If Windows complains of being unable to read the drive or wants to format it first, click 'No.'
5. If the steps in Windows failed, your final option is to use the command structure beneath Windows to try to fix the drive manually. Click the 'Start' button then type 'cmd' in the search or run area to open up a command prompt.
6. Browse to your flash drive's directory by typing in its drive letter followed by a colon: for example 'k:' If you do not know your drive's letter, experiment to find it starting with the letter 'E' if you have a single CD-ROM in your computer (which is usually 'D'). Go down the alphabet until you get the message: 'The System Cannot Find the Drive Specified.' The last drive letter you got is probably your flash drive.
7. Type in 'chkdsk' at the command prompt and wait for the check to complete (it should be fairly quick). If check disk finds errors, it will offer to fix them. Choose 'y' at the command prompt and it will repair the drive.