DO NOT DO WHAT IS LISTED BELOW!
1. Install on New Machine
2. Once Prompted, Call Microsoft
3. Say You uninstalled the software from the previous machine even if you haven't
4. Enter the new code they give you
5. Your new machine is up and running!
Since your other PC is running the same windows, it is still activated, to avoid calling Microsoft again and redoing the above trick, backup the WPA.DBL that is in your C:\Windows\System32 . If you ever reinstall on the old system, after install, DO NOT ACTIVATE! Re-Boot into Safe Mode and copy over the WPA.DBL to the new System32 folder and if the HardWare is the same, Windows will read as activated.
Do not do anything listed above! It is listed for Educational purposes to show that even Microsoft's somehow "fool-proof" plan for activation is easily by-passed with a Simple Phone Call to their own company!...
Dual License do only incude Office afaik. Windows is a Single User License, unless you have Volume Licensing.