Assuming from your first post that there wasn't a BSOD, please go through your system logs; if you remember the date/time when these events happened it will be helpful to look for logs for entries accordingly. You can find your system logs in Control Panel, Administrative tools, then click on Event Viewer.
Blue Screen of Death
Blue Screen of Death
No, something has caused it to reboot. Opening software shouldn't cause such an adverse reaction, unless something critical is failing, in which case it would BSOD.
If its not a BSOD, it could well be your PSU failing - The only way to test that is to use another PSU in its place and then check its behaviour.
It could also be overheating. Remove the side panel (with the mains lead switched off at the wall), and hold the chasis frame for a sec or two to discharge any static electricity your carrying, and then check the CPU cooler, the external fan, and the fan on your graphics card - If they're really dusty, use a paintbrush to clean all the dust off them (or you can buy a can of compressed air to blow it off too).
I dont think its getting hot i keep it pretty clean and dusted. What is the PSU? As i say its only done this about 3 time in the past 2 months.
PSU = Power supply unit
Clean and dusted inside of the cover though yeah?
Have you taken time to look at the system logs?
One of Leeky's argument with regard to PSU make sense, if its an OEM machine, I am sure it will have a cheap 'that will do it sort of PSU'. Therefore, PSU degradation can be an real issue as well.
Can you please paste that information with Event ID number here?
Go to Event Viewer again, and click on Windows Logs, then first to system log, and right click on it, select Save All Events As, give the file a name, and it should be saved with evtx extension, repeat the same process for application logs, and post both of the saved files with your next post. Regards