what the Stop message means, but you will need to do some more research to track down the problem.
Stop: 0X00000050 can relate to physical memory problems, or software problems such as anti-virus software. It could also be other hardware problems such as a video card. The site below has more information. Scroll down to 0X00000050, (note, this is six 0's then 50, not seven 0's then 50).
The site has some links to a troubleshooting guide and other articles.
For my part, I would suggest a heat problem. You say it can run all night without problems, (cooler at nights), But it shuts down at some time during the day, (hotter during the day?). If that is the case, it could be an internal fan struggling to get rid of the heat. You could open the case and run an electric external fan on the circuit board to cool it down, and if you have no problems you may have pin pointed the cause.
My computer is shutting down, powering off on its own. I start up my computer in the morning 7:00 AM or so and always around the same time it shuts down, like someone pulled the plug out. It then tries to reboot and will continue shutting down. After I leave it for a while it will operate ok, but maybe after 15 minutes the same process will happen. If I leave it off and then turn it on say in the evening, it will stay on all night till late morning or so. I turned off my automatic reboot and got the blue screen with the following message:
***STOP: 0X00000050 (0XF7574655, 0X00000000, 0XE1ED4B54, 0X00000000)
BEGINNING DUMP OF PHYSICAL MEMORY
I AM OPERATING ON XP HOME EDITION WITH SP2.
MY COMPUTER IS E MACHINE WITH AMD 1.79 GHZ, 480 MB OF RAM AND 90 GB HARD DRIVE.
FYI, I can operate in Safe Mode all day long, no prob. Any ideas.