The probable problem could be with source disk, not with destination one... If disk is 50GB but it's not extended to max capacity but occupied something like 15GB - this is a problem - shrink the disk size, ex exend it to maximum size.
About "The access to the host resource is restricted..." you need to point as target the VC server which manage the ESX.
About hosts file - this helps when you access by name destination VC and/or ESX which are not visible in your source machine, to avoid this use the IP addresses.
The location of the file is c:\windows\system32\drivers\etc\hosts and adding the name-to-ip resolution is very simple, just edit it with notepad (running from elevated administrator).
HTH