My Maxtor OneTouch 4 Mini Portable Hard Drive is not recognised by my Laptop

I had this problem a day ago, I was using my laptop with my portable hard disk connected. It seems that my laptop was running really slow so I got frustrated and shut it off directly by holding on to the power button. When I restarted my laptop I couldn't get my portable hard disk to connect, every time I try to connect it there is an error message at the task bar that reads "USB Device Not Recognized" but the power still runs but not for long and goes off after a while. In addition, there is no icon of the portable hard disk in "My Computer" neither in "Disk Management".Though my operating system (Windows Vista Ultimate) opted mi to format my portable hard disk and didn't format it because i have important data in there which i can't afford to lose.

Right now am really worried and looking for ways to get it up and running again.

Can you help me out?:sigh: