total freeze

my laptop keeps freezing. i have done all the scans and nothing is found. i have avg 7.5,spywareblaster,ad aware se personel,avg anti spyware, spybot,cc cleaner,system mechanic 7,and advanced windows care v2 personel installed and it still freezes. even the task manager wont work all i can do it turn it off and turn it back on again. it happens if i am on the net or not can anybody please help. you have helped in the past with other things for me.i am most grateful for forums like this.:cry