You're not going to be able fix this via an internet forum, like AAM.
It's a bit like asking 'What can I throw out of my shed?'. I can't help you with your shed unless;
a) I'm standing at the shed with you, so I can see what is in there, and
b) you are standing beside, so I can ask if you are still interesting in kayaking, or gardening, or whatever.
Your best bet is to get someone who knows a bit about computers to sit down with you and go through the stuff. If you can't arrange this, you can go through the files and folders, and delete whatever stuff you recognise. If you don't recognise it, then don't delete it.