what /how do I back up?

Linbox

If you have backed up all your important documents, email, bookmarks, etc. I always backup my email and browser to a portable edition therefore lose nothing, using SyncBackSE - maybe this is a bit of overkill for your needs.

Next would be your operating system. The easiest/best (and free) at the moment is, Macrium Reflect™ Free Edition Remember that you cant backup to the same drive. But you could backup to your USB drive if you have enough room.

If you can install a program like a new browser and use a program to save documents - like word, you should have no problem using Macrium.