Disk Utility Secure/Erase Options Greyed Out

My daughter had a Mac laptop that was given to her by a friend a long time ago. The friend had a small tech business and he would do all sorts of weird things to his Macs. So normal things often didn't work as expected. I just want to recycle the Mac. Give it to a school if anyone wants it or just trash it in an enviro-friendly way. But I want to make sure all personal data is off it first.

So I opened Disk Utility planning to delete all files. First of all (I think this is an example of weirdness) two disks show up in Disk Utility. One says "74.5 GB Fujitsu MHT20..." Then directly below that it just says the standard "Macintosh HD". When I click on either disk in Disk Utility and go to the Erase tab all the options are greyed out. So I can't click on "Security Options" (I think that is where I go to securely delete everything) and I can't click on just "Erase". The volume format for both disks is "Mac OS Extended (Journaled)". I think (but not completely certain) I have admin rights with the login I'm using. I've done other things that I believe normally require admin rights.

The Mac is running OS 10.5.8 (note its not listed as one of the Apple devices I normally use because its not, its been sitting on a shelf for years). Any ideas? Or should I just resort to a hammer or big magnet?