100 gb data missing HELP

Hey, if anyone could please help me i would be so grateful. Right now i am gone from my desktop for some while and am using my hp laptop. After installing and uninstalling and repairing (ETC... For technical reasons with the application) Steam a few times i got it working again. I started updating it and when it was halfway finished i went into my computer and saw 100 GBs of files missing. I cant clarify which because all my folders for Game applications and software are still there. I have checked some such as Atari NWN2 and the Sims2 (brothers) and it seems like the files are there. But it still says on my computer that i have over 100 gb of space remaining, when i used to have about only 8. So i decided to give the Sims 2 a try to see if its still there. The autorun Splash screen still appears and i click play. I wait around 10 seconds until an empty prompt only with a red X symbol appears! i press OK and it doesnt start up. I have restored my computer to the farthest it can go which is pretty recent. The installing of steam, although it still wont work(only refreshed the pictures of my application shortcuts when before it couldnt even locate the source locations). I take that as a hint to the problem but i cant be completely sure. If anyone knows a solution please let me know and I will be very grateful.

My info (that I know basically since it is a new notebook) is that I own an HP SE dv6700t Entertainment notebook. The operating system that it came with was Windows Vista Home Premium 32 bit. Sorry that is all i can think of giving you.

P.S: The data missing might have occured when i did a fix installation on trial 3ds max 9 right before Steam Installation. That appeared on the system restore list after the 1st one i made. I have done about 3 restores and it doesnt fix it.