open an external hard drive without formatting

[JKK200]

my external hard drive is asking to be formated but i want the data inside how do I open it without losing the data?

 

[Saga Lout]

Assuming a Windows system (Linux wouldn't throw that erro rmessage) open a Command Prompt and type
chkdsk x: /r
where x is the drive letter of the external. That should run a five stage process that finds and tries to fix any disk errors and it may make teh disk show up properly in My Computer next time you look.