i can´t answer all questions (someone else will do this for sure) but did you have an
antivirus program (up to date + scan)
firewall
anti-maleware (up to date + scan)
?
these would be the first steps.
agreed. it seems that you missed the first step.. i'd include a complete wipe and defrag. Updating the system to patch level is questionable if you dont know what you are doing -- being that the initial step requires and internet connection.
Umm, what would a defrag do in this case, this doesn't seem to make much sense. Just create a wallet on a computer running a live CD! It doesn't need the latest updates, why would it if it will never be connected to the internet!