Windows 7: Windows 7 Wants To Format My Back-up HD

G'day,



I have been running MS Windows 7 Home Premium 32 Bit for around one year and I have had few problems...Till now! I use USB Flash Drives and a 500GB WD external HD to store important programs, (Programs and information I have bought and downloaded over the years)
I decided to store all my bought programs on the 500GB HD...Along with my images created by Windows 7 Back-up...Doing so has worked well...Till last week when I did my last back-up session! (I do a back-up each time I do a Windows Update or add a new program/s) Windows 7 started the back-up but after twenty minutes or so, Windows reported that the back-up had been unsuccessful. I checked my external HD and there was lots of space for the back-up image so I have no idea why the last back-up was unsuccessful. I shut down my laptop and thought I would check on the problem, or do another back-up later. When I started my computer later that night, plugged in the external HD, I got the message, “You Need To Format The Drive F: Before It Can Be Used” I closed the message box as I have no wish to format my external HD and wipe-out all my, important-to-me, information and programs.
Can anyone here instruct me on any way I can get to salvage whatever programs and files that can be salvaged from the external HD before I format it. I have tried the external HD on two other computers, one running Windows 98, the other running Windows XP but none can read the external HD. The last Windows 7 back-up truly stuffed-up my external HD.

Thanking you in advance for your advice.

Bill
Australia