There are a lot of things that can cause RAW/unformatted warning issues with flash drives.
First of, try plugging the drive into another PC, backing it up and reformatting it then connect (the now empty + reformatted) drive into the problem PC.
If that doesnt work, open disk management, if your disk is listed in the window under volumes, select it and see if the memory view shows a healthy allocated partition. If it doesnt you, can use this information to do some more relevant searching on Google as again, it may be a lot of things, but there is plenty (like, tons) of already answered questions on forums about such.
If you still have a problem, open device manager and look down through the list of devices under the headings disk drives, storage controllers, system devices and, most importantly, universal serial bus controllers. If any of them show icon overlays such as yellow question marks or exclamation marks or red x's your problem is likely with the device driver (if not with the device itself). Again armed with this info you should be able to find plenty of info to solve via Google - the usual root being to use the windows wizard to either fix or uninstall and then re-install the driver - though you should be careful that you understand which driver you are uninstalling and why before you do so as you could end up bricking your system.