How can I recover "temp" files deleted off my external hard drive?

I use Picasa Web to upload pictures from my digital camera, and I'm in the process of using an external hard drive to transfer my pictures to a new computer. My current computer is out of memory so I hooked it up to an external hard drive and set Picasa to automatically download my newly uploaded pictures to the "temp" folder in my hard drive. Well, I accessed my external hard drive software today -- WSync -- and updated the software because it asked me too, then I checked and my temp files aren't there. I know I shouldn't have put them in temp but I wasn't thinking. How can I recover them?

Servant Salamander is a good recovery agent.

Temp files are just that if you do anything to the hard drive, (update software) they will be deleted, try and do a general search on the external drive for *.jpg , *.gif-----etc....... if they are anywhere on the drive that command in search will pick up all photos and display them...

You can also try Recuva,(free download), I found it on ntlworld.com, put recuva in their searchbar. Another user on this site suggested it is how I found it. (they list three different free downloads)