Internet Keeps On Freezing / Cant Install Firefox Or Any Program

i have comcast internet.usually this problem occurs when im on Internet. i use google chrome. whenever i browse Internet, in like twenty five minute of video watching my computer starts to freeze. there is a cicle spinning and screen becomes blurry. i cant do alt control delete to end task it, because nothin pops up when i click it. now when i use other sites like facebook, twitter, the internet starts to freeze like before, before it was only Internet, now its a lot of sites and i have to manually hot the power button and relogon. is it a good sign that my power button on monitor doesnt turn blue when i turn it on, it used to , but now it dont. i can not use firefox because it will not let me install it. i am an administrator for sure because i followed these steps.url...when i google mozilla firefox from google chrome, and install it, it says"you may not have the necessary permissions to use all the features of the program you are about to run. you may run this program as a different user or continue to run the program as the current user."when i click towards current user, my name and my last name initial is there in parentheses after the word current user although my account name is different. then its all gray at the bottom and under user name it says administator, and blank under password but i cant make any changes because it is gray. if i click okay, it disappears and nothin installed. and when i click at bottom run this program as the following user and then i see administrator under user name and nothin under password. the account i have is protected by a password. if i type in my username and password that i currently am using, i have one account on my pc, or if i press okay how it was given to me, it says logon failure: user account restriction. possible reasons are blank passwords not allowed, logon hour restrictions, or a policy restriction has been enforced."i use superantispyware,malwairebytes pro, avast free as a virus protection.and whenever i go to itunes, i have to end task it once because it always freezes on me the first time i access it, it does let me end task itunes though