SONYVAIO VGN A197VP unpredictable shutdown

Hello,
I have an old Sony VAIO VGN A197VP< it strarted with unpredictable shut downs< just before the shut down a blue screen message is displayed, about a memory dump. Than it starts with memory dump. And thats it. Have to resart it all over again. Sometimes it works fine for hours, sometimes shuts down after few minutes.
Took the machine to professional service, we changed the hard disk with a new one and reinstalled all the drives. The guys at the service say that there might be a problem with the hard drive controllers< anotherword, it is probably more expencive to repair than to buy a completely new lap top. I do not know.
Just love my Vaio and refuse to believe this. Anyone with similar problem, please help....Regards, ICEPOP

SONY VAIO VGN A197VP, Windows XP Propfessional, Internet Explorer 7, RAM 512, Hard disk IDE 160GB