Programs/Files Disappearing

Hello, I'm having a problem with programs disappearing when I log onto different names, and then log back onto the name I installed the program with. I installed a game, and the next day when another member of my family logged onto his name, and then logged back onto my name, the program that was in my start menu's accessories had disappeared. The folder it was in said empty. I then went to uninstall it, but where it used to say 1.4 gigabyte, it now said 11.08 MB. I continued to uninstall it, but when I did.. my diskspace had only been added 11MB instead of 1.4GB. I did it several times trying to fix it, but I ended up with 1.80Gigs, instead of what it should have been if I uninstalled the whole game. Now I have several games that won't uninstall (The Sims collection) and none of them show up anymore. I would really apprieciate help with this problem. Also, I cannot find any of the excess program files that the uninstallation should've left behind. Thanks

 

Have you run a virus scan recently? Using current def files?