500 GB WD external hard drive not mounting. My 500 GB WD studio edition external hard drive no

Question

My 500 GB WD studio edition external hard drive no longer mounts to my desktop (Apple Powerbook G4). I had it for only 3 months. It turns on and runs properly and when I check it's status in Disk Utility it shows up fine but I can't get it to mount. I have about 50 gigs worth of photographs on it and I desperately need to access some of the files A.S.A.P. Please help.