You should purchase additional disk space. You should also think about better organising your data. You should keep programs and operating systems data away from personal files (documents, mp3s, movies, etc) and keep personal data on another drive.
I do not believe that you have 36GB of applications on there, so it must be because you have personal files taking up that space (Pr0n??). Or perhaps lots of games. Anyway, get another HDD and copy all of your personal files onto that. A 120GB HDD is fairly cheap right now, get one of those. Post back in a new thread if you require help fitting and configuring your new drive. Consider a dedicated games partition as well, if you have to reinstall your OS you don't have to reinstall all games and then repatch them again.