USB drives are one of the prime reasons for spreading of viruses as we use it in many PCs, so there is chance that it might be infected with Viruses and which in turn effects other PCs as well. The USB Protector is a freeware application which prevents write access to a USB drives. This will protect USB drives from viruses, malwares, spywares etc.
USB Writer Protector is a portable program available in different languages and also easy to use. The file is only 190KB in size and supports on Windows XP.
If you use your USB drive on multiple PCs and on PCs available in Internet cafe, then it better to write protect so that it prevents viruses getting into the drives. USB Write Protect is worth trying.