What errors do you get? Does your system allow you to access the pendrive? These devices are generally factory formatted with a FAT file system which can be read by Windows, Linux, or Apple system. If you cannot access it, then it is likely a problem with your system software. I used to get this all the time with Windows 7 and had to remove all the USB devices from the device manager, and then reboot the system so it would reload the drivers and such. This was a regular PITA that I, and others, had to go through.
If your uh, USB has a letter (let's assume it has letter B). Use following commands:
select disk X
format fs=dat32 label="My pendrive" quick
assign letter Z
Don't just copy this, just copy-paste this LINE BY LINE. After list disk, you will be given all the disks connected to computer, replace X with your "disk-number" which in this case is an USB. After this, your pendrive should be MY PENDRIVE (Z:), if it won't succeed, we hear it from you.
Warning: Be careful with this. And you will be just fine.