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 shit 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 shit 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.