Hi, I have Verbatim external drive with storage size of 250 GB. It worked normally all the time, but today a message appeared. The message said that the USB is unknown. This is really importnant to me and please don't suggest formating, because I have imprtnant things on it. Thanks.

Have you tried it on another PC?
If you really can't get it up and running in Windows I would try it in a Linux machine to retrieve data. Other than that you could always disassemble the hard drive and add it as a slave to a desktop.

I didn't try it yet, but I forgot one thing. It has led indicators when its turned on. The indicators turn on, and I hear the fan worknig normally. I will leave the ''slave'' option as last one, because I don't want to disassemble it. Thanks for suggestions.