Hello, I have a Western Digital 500gig external hard drive (model wd5000c032) which I'd like to completely reformat to use with my macbook pro and Time Machine (running os 10). As it is now, my mac can only use 147 gigs, and often gives an error message saying it needs additional space to backup. It was previously used on a pc to hold pictures, but I doubt it used anything near 357 gigs for that. Is it possible to reformat the entire drive, or has a portion of it been un-reversably formatted for the pc? Thanks for your replies.