Windows 7: hard drive needs to be formatted

Hello,
I borrowed my friend's external hard drive and a I first connected to my PC it was working perfectly. Yet the second time I tried to my PC recognized it but couldn't open it & it kept giving me the message that I need to format the hard drive before using it.
I tried many time on different computers & I got the same result.
Is there any thing that I can do!

Try a chkdsk /r

How did you remove the external hard drive from the computer? Did you use the safely remove icon in the notification area? If not this can some times render the device inoperable.

How to 'Safely Remove' Devices | PCWorld

This is straight from MS....

Safely remove devices from your computer

whs I'll try it, thanx

yes, I used safely remove icon.

I see this a lot with PCs that do not supply good power through the USB port. Most typically with the external drives that are only powered by the USB port (without a dedicated power supply).
So the first thing to try is different USB ports, particularly the ones in the back of the PC, connected directly to the motherboard.

Another thing to check (I had this occur with my own Seagate FreeAgent GoFlex) is the physical connection between the plastic outer shell (where the USB cable plugs in) and the actual hard drive. I found that this can get loose and the connection gets bad. By reseating that part and making a firm connection it cleared up the odd issues I was having.

Check those, let us know.