fugem,
I would agree with Dave, more than likely this is being used by System Restore. You can always delete all of your system restore points (except the most recent by doing a disk cleanup then clicking on the Advanced Tab. You should see a button that says something along the lines of, delete all restore points except most recent.
Then you may want to limit how much space System Restore is allowed to use. To do this, right click on MY COMPUTER, then Properties. Then click on the System Restore Tab Then click on Settings and adjust accordingly.
Also, 35 GB is quite a small hard drive nowadays. I have a 300 GB hard drive and I still am running out of room.
