How to avoid formatting drive

What did you format to,fat,fat32,NTFS,

I am not sure if your saying you had it on a desktop pc and now you plugged it into a laptop, or its always been on the same computer
and it just wants to format.

Either way, a computer should not want to format, usually you have to tell it to format, and the only reason to format a hard drive whether internal
or external ,is to change the file system from one to another,

example; FAT to NTFS , or your going to install a operating system to the hard drive.

Its sounds like you had it in a computer whether the same one or a different one, and you did not use the safely remove hardware, or you unplugged it while it was writing data back and forth.

Turn both off, the computer and external hard drive, plug the hard drive
into a different USB port, or firewire, how ever it connects.

Now turn on the external hard drive, wait a few minutes, now start the computer, once in windows if you see this I want to format you hard drive, tell it no, go to control panel and open devise MGR, and look for a yellow shield, under Universal serial bus controllers , the one that has a yellow mark, right click on it and choose properties, read what it says
in the open box, if it says disabled, enable it, if it says no driver,
click on driver tab, and click update driver.

Well u can right-click on the drive\properties\tools\use check disk to fix errors etc
However if it doesn't work, try access it from safemode pressing F8. U can also access through other OS.

You can recover data from the "not formatted" hard drive, here's a good data recovery guide:
fix hard drive not formatted error

hope this helps.

Odiebugs what is MGR under control panel? i have windows7

Your MFT ( i.e file allocation table) has been corrupted.... try using recovery softwares like scand disk and stuff.... my advce wud b to consult an expert data recoverer cuz chances are not great(trust me).... next time keep ur hard drive safe from magnetic and other such fields