laptop keeps shutting down unexpectedly......

Hi my laptop keeps shutting down unexpectedly, tried to do a virus scan with trend micro but shut down each time before completion. a complete novice to the techno world! so could i have any advice in lay mans terms please.

Thanking you

Jackie

Please download the current version of HijackThis from HERE

• Double click and run the installer.
  
• It will install to C:\Program Files\Trend Micro\HijackThis\hijackthis.exe
  
• After installing, you should get the user agreement, press accept and Hijack This will run.
  
• Select Do a system scan and save a log file. This will open a notepad file of everything Hijack This found, copy and paste it back here.