over heating laptops?

Not sure if anyone else has had this same problem i have a one year old laptop which cost me over 300 it seemed fine for a few days then the more i used it the more it went crazy?

I have the recipt for my purchase but the store says its not their fault and that i caused the problems myself!I thought maybe i could try and explain or take the laptop to a shop to get loked at and to prove it was nothing i did to it. so now im looking at wasting my three hundred pound plus the extra i paid for the insurance.

I was wondering if this is a common problem and couldnt find much on the subject online to help me out either and have asked around on chat forums and a few other well known computer error sites.

Even tried to change the battery and the fuse in the charger but still no help with the problem. Am thinking maybe i should have kept my money or at least picked a laptop that workes and comes from a store that will refund and keep to the policy the claim they offer.

It started to go slow at first but put it down to my connection. I charged battery up for two hours a day then things went wrong i could only keep power to my laptop by keeping the mains plugged in.

Then it started to get real hot and kept shutting down mid way through a site and then losing power altogether? had to unplug it all for a few hours to get it back on an cooled down but then only lasted a few mins and am scared it may ruin it completely and will have no power as may be affecting the battery pack the more i try

Im sure its not a virus and have paid out forusb fan and a tray but no change.

Am thinking maybe i should have kept my old pc they seem to have less problems. Would be happy to recieve any comments or advice that you may have or what rights i have to trying to get my full refund back as i seem to have no knowledge on computers or my rights in a shop although my reciept says i get ninety days this seems to not be the case now.