If it's not clear what types the different files are he may be trying to open files as text which aren't actually text (try opening a picture file with a text editor and see what you get!). The files he's trying to open may be pictures, or database tables, or Word documents, or...
I'd be inclined to get authority from someone at your school to take the drive to a disk recovery specialist. I'm not quite sure how they do it, but they have some specialist machinery and techniques for reading scrambled data. Don't let your IT guys play with it any more - they've done enough damage already, and the more they mess with it the less your chances of getting the data recovered. Above all, DON'T let them try to defragment it or run scandisk/chkdsk.
If you can get your uploaddata folder (and its subfolders) and your database recovered then you should be able to nail them into a fresh installation of Moodle, or even if you just get your files back you can then upload them one at a time into a new installation.
The fact that your IT guy can get the disk to show something is encouraging - the drive clearly isn't completely dead, just badly corrupted. I think you need professional help with this now - have a look in your Yellow Pages under "Computer Disaster Planning", or something like that.