Mbr = master boot record,
Basically it is the very first part of the Hard Disk Drive.
A little program responsible for starting the rest of the operating system
Anyway, there are many 'lightweight' distributions
Linux Mint xfce is worth looking at
Should be easy to install and suited to your old hardware.
The interface won't be a million miles away from win XP/7
Regards breaking up quotes
They wrote this
Rest of post
You add the lowercase quotes (but case doesn't matter!)
Edit: make sure you spell/type it correctly,..,( I hate phone keyboards)