new computer suddenly shuts down

I built a new computer with Shuttle AV18E MB. After about 15 min. ,it suddenly shuts down and it won't power back up. Only after taking the power cable out , and some trying it will come back on but then it will shut down again..
celeron 400
128MB

need help
thanks

 

sanjiv428
Welcome to TSG!
Just a thought. Are you having an overheat problem or power supply problem?
Dave

 

i'm new to hardware checking.
how can I check the power supply?
thanks

 

I usually take them in to a shop and have them run it on their equipment. Last time I did it it cost me $5.00 for them to check it out.
Dave

 

thanks Dave