next-gen wrote:I have tried both USB slots, but neither of them work.
What can I do if I dont have an extra USB drive?
Did you try just unplugging the USB disk, waiting a few seconds, and plugging it right back in as Kad suggested? What you describe is a well known issue, documented in dozens of posts, on the FAQ and on the Wiki. 99.999% of the persons with that issue resolved it by following those simple steps.