Agreeing with what TheCompWiz and typoknig wrote about Windows. Assuming the two systems use the same processor series and mount their hard drives and other devices at the same mount points, you may very well be able to simply copy the Ubuntu partition over and have it work.
If you do reinstall Ubuntu, you can get a list of installed packages with
dpkg --get-selections > selections.txt
Then to install those packages on the new system, copy selections.txt over and:
dpkg --set-selections < selections.txt
You may have to add some non-default repositories, but since you already use Ubuntu I'm assuming you know how to do that.