Why does my computer keep shutting down?

It only happens when you are online? Sounds like either a bad NIC or a virus. May also be other things, like the power supply or just plain old dust buildup causing heat inside your computer and forcing a shutdown when the extra power demands of the NIC raises the temp past the critical mark.

It may have Parental Controls enabled... There, you are able to shut down the computer after a certain number of hours on the internet or connection.. Check that... If not, then I don't know... But that is what is sounds like!!!

the overall rule the following is that if this happens randomly, that is likely a hardware subject. If this happens always that is likely application. in case you've put in application those days, you may want to favor to objective 'equipment fix' to flow decrease back to a time at the same time as it became operating. If the laptop might want to be overheating you are able to obtain application to ascertain the CPU and board temperature. those might want to not exceed 70 stages c or 50 stages C respectively. you are able to also favor to look interior and be conscious how dusty that is as this stops air circulating suitable.

sounds you have some sort of malware infection, this should clean it up for you

http://www.superantispyware.com/