iMac G4 Hardrive Crashed

My old iMac g4 crashed about a week ago, i had someone pull my data of the mac hard drive and put it on an external. The external drive is and omega portable 500gig. When i plug my external drive into my iMac i can see all my stuff is there, the trouble is none of it will open. When i click to open a file a box opens saying "could not open ___ because it is either on supported file type or because the file has been damaged" (I've tried many different file types none of them will open). If it so happens that these files are damaged is there any software that i can install to help fix the files?

If you have the original HDD, you can send it off for like $500 (not worth it ) So, just get a new HDD (hopefully one that won't crash, and do regular backups w/ carbon copy cloner