recovered jpg files still not viewable

[tsoimp]

I have some jpg files deleted from an external portable hard drive one month ago through my Mac OS 10.6 desktop. When use R-studio for Mac to scan the same portable hard drive, all those deleted jpg files were found with red crosses to them. However, they are not pre-viewable. I purchased R-studio for Mac and successfully recovered them. All the file sizes are correct. However, they are still not viewable. What can I do? Anyway to repair them?

[Alt]

Try to scan the hard drive. See R-Studio on-line help for more details.

[tsoimp]

If deleted files are not preview-able, does it mean they are not recoverable?

[Alt]

Unfortunately, most likely yes.
Looks like the data on those files has been overwritten. Did you write much on the disk after you had formatted it?
You may also try to find some your files among the known file types (Scan results - > Extra Found Files).