Lets say you live in a world where the world government has decided people are getting too addicted to the internet and ordered the internet to be shut down for 5 years. The 100 GB of storage is all you have (excluding essential system files for your Operating System). You have 24 hours before the internet is getting shut down. What do you download?
First thing would be to seriously look into data compression, and live with heavily lossy-compressed media (my music collection would be ring-fenced though). Throw out backups of physical media (take the chance on disc-rot); I guess any backups wouldn’t be possible in this universe anyway so it will all be left to chance. And then see what’s left.