network disconnect

HOHKAY SO i'm helping a friend of mine try to fix their new computer that has been having an issue where the internet connection will cut out on the machine seemingly randomly despite being on an ethernet connection. i would 100% suspect the router if not for this issue only happening on this...

For some months we've not been able to access our Maxtor 500gb external hard drive, nor to back up files to it. We run Windows 7 on our PC. We get the system message that the relevant drive or network connection is not recognised. What can we do, please?