My Laptop Keeps Randomly Freezing

Hello,

I have a 2 year old HP dv6000 series laptop running Windows Vista. I was having problems with it randomly freezing where I could initially move the mouse and just not click on anything, then not being able to even do that. Control Alt Delete didn't work or anything, I had to hold the power button to restart it (which I hate doing >.<). After running chkdsk, memory tests, seeing that it wasn't overheating, and running several anti-virus programs, I finally decided to just completely start anew as this problem just started a few months ago. I recovered my computer to factory settings and still I'm having this issue at random times while using random programs. I don't have any big files on here or any big programs, I just use it for school basically and surfing the internet on reputable sites. Does anyone have any idea how to find out what could be wrong? I've tried everything >.< Thanks for your time.