External Hard Drive Not Detected When Connected To PC

I recently purchased an Iomega 1TB external hard drive to back up my files from my Laptop (Toshiba satellite) because it has been constantly showing hard drive failure warnings and messages telling me to back up my files. When I connected the hard drive the first time, it worked fine and I was able to access it, but didn't use it for anything at the time. The next time I used it, however, the usual "New device" sound didn't play and the hard drive didn't show up in the file browser. I then looked up the issue to find that it is a common problem where the device hasn't been assigned a drive letter. I went to the Disk Manager to fix the issue but the device was not in the list of connected devices.The problem seems to be with my computer because it works fine on my brother's computer and has no issues.Additionally, I have been having problems with Windows Update being stuck on "Downloading 0%" and have had to use the system restore several times when getting stuck on an update message on startup. I think that this may be the cause of the problem (and yes, I have turned on the hard drive).