Desktop? laptop? sits on the table? sits on the floor? First guess would be it's overheating. Have you ever opened it up & blown out the dust bunnies?

It is a new Dell Desktop. I really don't think it is overheating. I am thinking it has something to do with Windows 7, maybe doing upgrades and shutting down, but I would like to be ask before it does.

To stop auto updates in Windows 7 click Start
click Control panel
click System and Security
click Turn automatic updating on or off (this is a sub header under the Window update tab).
Do your thing.

also could be under power saver controls, set them all to off if any mention a time it will shut down or go to sleep etc. You can google power saving mode in windows 7 to find out more

Thanks, if I turn the updates off, will it let me know when updates are available?

Make sure you are using it on a solid surface, not your lap, ontop of the bed etc..as it blocks the fan vents and will over heat..

yes it will have a pop up down by the clock, be sure you do not have yours in the hidden icons thing if you do you can move it down onto the bar so you can see it better.
Just make sure when you make your choice you pick the one that says notify me do not install or something like that.

Thanks so much. I followed the advise given and it has not shut down since. I really appreciate your help.

""Make sure you are using it on a solid surface, not your lap, ontop of the bed etc..as it blocks the fan vents and will over heat.."" LOL at me...I could have sworn I seen a laptop mentioned..oh well..lol