You have a Thinkpad? As far as i have heard their linux compatibility is fairly good.
An yes, ubuntu won't have more problems than windows with low power devices.
My old 4GB ram, 1.4GHz 4 core laptop ran linux mint fine.
Ps: linux mint is a ubuntu fork, and has a desktop interface that looks a lot like windows (example: in the bottom left there is the linux mint logo that you can click to open the start menu like on win 7).
If you have a legitimite minecraft account, you can use multimc (and probably prism) to launch a game in offline mode (and choose a custom name). This works for example if you want to play with a friend in a lan world.
Solution in ruby
This is my third program in ruby after the ruby tutorial and half of the rails tutorial, so don't expect anything too good from it.
Also i did this today since i had time, i will probably not comment every day.