HP Pavilion Dv7-6166nr Keeps Freezing?

I have a dv7-6166nr model and i have been having problems with it. Recently the vendor i bought from on ebay did a fix on it cause before it would freeze one i start up. it wouldnt let me open no programs or nothing without freezing. well like i said he done a fix and it was good it lasted for 2 months until I had to restore it to factory settings cause some of the files got corrupted. So now that i done the factory reset it went back to its old self but this time different. It wasnt as worse as  before. This time it lets me open programs and surf the web(Note: every once and a while it freezes when i surf but not often) but theres one problem.... i cant download anything for my notebook. Once i try to download anything like a antivirus or anytype of program it goes back to day one when it used to freeze. Now overall it runs good but i cant maximize its use cause the darn thing wont let me download anything. It even sometimes freeze when i push the start button or sometimes when i open a program but it rare. ive done every support method almost like disc defrag and i used the hp support program and it still wont run the way i want it to. Some help would be nice please because i start school soon