Hard Disk Not Working

Hello,
Hi,
I have a Portable Simpletech Pininfarina 120 GB hard disk. It has two lights. A blue one which blinks randomly, and a red one which is on all the time. I have to connect it to the back of My P.c. because it only supports USB 2.0. And i don't know what happened, only the red light is blinking and the hard disk is not found on my P.C. while normally it does. and there's no spinning of the hard disk as there usually is. I am Really worried because This hard disk contains most of my hard work.
Thanks.