Freezing

I used to have vista and my Toshiba laptop started freezing a lot. I had someone put on 7 premium or pro and it still freezes. I had it cleaned a new hard drive put in and checked for virus and spyware. I start it up and within a few minutes it freezes. I crash it and then have to restart it then it runs fine for the rest of the time i'm using it. The next time I go to use my laptop within a few min. of using it it freezes again so I crash it and restart it and it runs fine for as long as I use it. So everytime I start my computer it will freeze within a few minutes I crash it restart it then it works fine but I'm tired of it taking 10 to 15 minutes to finally be able to use my computer. I obviously have a problem somewhere so where do I star or should I just say it's been a nice 7 years or so get a new laptop