Hi
The 4xx series was really power hungry GPU series… that is why even with additional cooling its a problem to get them working properly…
If you would fill out the SIGNATURE could say it sooner 
ucp.php?i=profile&mode=signature
one more option as one of last resorts, look for some local EXPERT that can CLEAN the inner part of your notebook as over the years there could be a LOT of dust on the fans inside of the notebook…