Raw means that it has not been partitioned and formatted, or that the partition and format information has been corrupted.
First question: Was there data on the device previously? Second question: Do you need that data back?
If you don't need what's on it, use the Disk Manager to create a formatted FAT32 partition on the drive. Open Control Panel - Administrative Tools - System Management, and go to the Disk Management tab. At the bottom, find the bar that corresponds to the flash drive. Be ABSOLUTELY SURE that you have the right drive! Right-click on the space and, if necessary, initialize it. Then create a partition with all of the space, and format it as FAT32. If a wizard comes up, you may follow a different process.
Of course, there is the possibility that the pen drive that got corrupted once is failing, and that you will lose whatever you put on it.