When you have problems with a Flash Drives being recognized on a computer it is usually because there is another drive on the computer already using the drive letter that the flash drive wants to use. Example our network drives use the drive letter F, unfortunately a lot of flash drives also use the letter F as well.
To get around this go to
Control Panel >
Administrative Tools >
Computer Management >
Disk Management (on the left hand side of the screen) >
Look for the drive that is your flash drive (on the right hand side of the screen). It may or may not have a letter drive associated with it (you can tell by the sizes listed. 4 GB flash is the one listed as 4gb) >
Right click on it and select ‘change letter drive paths…’ >
Select a new drive letter (R is recommended for removable flash drives) >
Select the Change Button >
Under Assign the following drive letter select the letter R >
This will allow the computer to recognize the Flash drive each time.