Trouble With Windows 8 Accounts

[Graceheart the Leopard]

I was on vacation for about a week. When I came home, my brother decided to log into my computer first, and for some reason, my old computer account was wiped, so he logged into my computer with his account. However, now all of my old files and programs that I installed on my account are on his account now, and when I tried to recreate my old account, nothing was on it. What happened, and how can I get my old accounts with my old files again?