My External HD Is Acknowledged In Disk Management, but It won’t work!

I have searched the internet, but I have not found a solution. I purchased a hard drive two days ago, and it worked fine for a day. After using it, my computer had trouble shutting off. When it turned back on, my hard drive could not be read. It would only come up in disc management, and it could not be initialized. Any help? This is a Satellite Laptop, and the External Hard Drive is a 500 GB Toshiba Canvio. I really need it to work, and I don’t want to go back to Best Buy. I just left from Best Buy to attempt to fix a laptop with no success. I don’t want another tech fail on my hands.. 🙁 Please… help.