Pentuim-D Overclocking issues

Ive got a pentuim-d 940 3.2ghz oc'd to 4.0ghz at 1.3875v up from 1.3375v and pc2-6400 800mhz at 1000mhz oc'd.

Now my problem is that windows runs stable though prime (Orthos) shuts down after about 7 hours of stressing the CPU and RAM, aswell avant keeps effing up and gets lagged and various other programs commit illegal operations and close. I havent tried games yet as per the simple programs closing, I figured bringing graphics into a somewhat unstable system was a bad idea, so what should I do? have I gone too far or do I need to change some settings to stablize my system?

In my experience everytime i have seen that illegal operation thing happen it means that your processor is overheating. What are your temps and what are you using for cooling?

temps are mid 40C's under load, ive actually backed down to 1.367v and 3.8xxGhz at 240x16

Since backing down are you still having problems? And what are you using to measure temps?

not reallyy no i think i could go back up to 4.0 and be ok im using pc wizard 2007 and cpuz, sometimes everest