2nd Hard Drive won't Initialize

I got a hold of a 20gig ATA hard drive to add to my G4 2x500 machine. I already have a 40 gig, which I partitioned when I replaced the original hard drive that crapped the bed. I put this second hard drive in as a slave. The computer sees it and gives me the stats and all for it, but it will not erase it no matter what I try. I got it from my someone who pulled it out of a PC, but it should work. I think it is a western digital and it looks just like the one in the machine now. Any help would be great....I need this second hard drive. Thanks!

 

Oddly enough, that didn't do it either. But I decided to boot is OS9 and try it there. And as luck would have it that worked. Thanks!