There are other likely causes of your laptop resetting... one of which could be that your Acer laptop uses an intergrated Intel graphics card (video card) which might cause it to reset on some games. The other cause could be the plugins you are using for PJ64. Heck, it might even be your Operating System.
Since overheating has been ruled out here, it would be helpful to know if you are on Vista or Windows XP. Who knows, Vista might have some issues with PJ64 (can't really say, as I only use XP myself). And if you're on XP, it might be the plugins you are using.
Have you tried playing ~other~ N64 games on PJ64? If so, do they play fine without causing a restart? It would help us try to offer better suggestions to help you play the games.
X-fi6: I'm sort of curious... are you using a laptop, or a desktop? My laptop is a Toshiba Satellite a60 series with an ATI card and is ~very~ prone to overheating and resetting (or just turning off) when I use it to play PJ64 games. I stopped using the laptop for gaming, and just stick to my desktop because it got to be a pain to have to save constantly and stop playing when it becomes too hot.