WIndows Vista frequent BSODS - unsure if it's malware or motherboard

I'm running Windows Vista 64 bit on an HP G60-243CL Notebook PC. Symptoms have worsened gradually, from slow handling of webpages to now, a week later, severe issues. Sometimes when I try to boot up my computer, it just won't do it at all. I'm left with an unresponsive dark blue screen hat shows a blinking cursor.

When Windows does load, the system performs (very slowly) for a few minutes, and then crashes to a BSOD.

At this time I can't download and run hijack this.

Thanks very much.