Error message: "Access denied", WD Passport 500GB drive. Permissions solution didn't work

I have a WD passport 500GB. It was working fine, but may have been disconnected improperly the other day and now I cannot open it. The icon appears as a folder and not a hard drive. When I click it it says “Access denied”. I have followed tips to take ownership of the drive by altering the permissions – has not worked. I can open the drive like normal on another computer, but no longer on my laptop where I need it urgently. 

I am running Windows XP Home. 

Please help.

I have booted in safe mode and given full control to my account (I am the only one on this computer and am the administrator).

Thank you.