It didn't cost you anything. You GAINED 1GB of free space if you went from 136 to 135.
What you really need to be asking is - does all your s**t still work, are you missing stuff you normally use, or have stored for backup in the past.
If you're really THAT concerned about it... Backup your important s**t to a CD/DVD/USB drive, whatever.. make sure its clean. Then just reformat your machine and put windows back on, or have a nerd you cheat off in class do it for you.