theres no possible way that i could guarantee a yes or no answer, BUT i believe you coudl do so very easily.
You can go ahead and perform a format, make sure you do a quick format.
Then you need to have recovery software such as:
"Active@ Uneraser"
"GetMyData"
"GetDataBack"
http://www.runtime.org/data-recovery-software.htm
"Ontrack easyRecovery"
http://www.krollontrack.com/resource-library/free-downloads/#data
There are other programs out there so google around, i've used those bottom 2 with success. Many programs out there will let you run a trial or limited functionality version for free, this will let you see what files are actually recoverable and you could then purchase the software at this point.
Make sure you arent installing this software on to the external drive! actually i would recommend that you install a software program or 2 first and try to simply recover a file you have deleted to see what software you like the most, and then give it a whirl and quick format your external drive