I plugged a external hard drive to my PC. My virus program showed that there trojan virus onit. I ran a scan, but stopped it before the scan was completed. When I plugged it in again I couldn't acccess the files although it shows the drive letter but noting under the size of the disk.
You have to make a decision first. If there is a virus on the drive, do you actually want to risk attaching it to your machine and possibly further infect your machine?
If you want to go ahead, it sounds like your drive has been corrupted, possibly by a bad disconnect and possibly by a virus (less likely, in my best guess without seeing it). How does it show up in the Device Manager?
Try a recovery program, such as Recuva or EASEUS, to recover what files can be found after whatever corrupted your drive. They are excellent if all that was damaged was volume / directory information and passable for more serious damage.