I agree with Kurt: As far as I see there’s no way of migration without any re-installation. And allow me also a remark: You will need one computer with (perhaps only temporary) access to the Internet.
With the approach, I already described in Relocate MiKTeX 2.9?, you can use the package base of your old MiKTeX installation. I don’t know, whether it works with a net drive, but you could mount the drive of the old computer to a local drive, too. Later you can use MiKTeX’ own update system, if you do at least a temporary connection to the Internet.
If you do not want any access to the Internet for your new computer, it gets more complicated:
You need a third computer with (temporary) access. On that computer download the whole MiKTeX repository to a local folder. The best would be putting this folder on a removable disk, but later burning of an DVD-RW is possible as well. The download can be done with the net installer, if you change the installation setting from default to "Download MikTeX" and select then "Complete MikTeX". After choosing the nearest CTAN mirror and download folder the download starts. It can take several hours depending on the connection speed. Later for performing updates of this repository
rsync is highly recommended, see rsync in the English Wikipedia for software suggestions, or at least
wget with its timestamp option.
When you start installation with the net installer on your offline pc, choose first installation from a local repository and select then the folder of the portable drive or DVD (especially do not choose “CD/DVD”, that’s only for shipped DVD’s from the developer). Attention, this path is saved in MiKTeX settings!
You should later perform updates for MiKTeX on your offline-pc on a regular basis for bugfixes and new packages.
If also on computer with internet connection MiKTeX is installed, updates should be done with the local repository, too. This saves a lot of bandwidth.