Computer turns off while playing games

what games are you playing and on what settings?
Also, what are you PC components? (CPU, RAM, GPU, PSU)

what temps ?

and what power supply?

I m playing Splinter cell double agent, virtua tennis 4, nfs hot pursuit

PC configuration
i3 processor 2.53 GHz
3 Gb ram
1 GB graphic card

above 78 C

i think your CPU;s temperature is to high...it may collaps for that it automatically turn off for that"

how can i fix it

Your CPU temps are way to high and it is going into thermal shut down. First make sure the fan is working and the heatsink is seated right. If the computer is dusty I would dust eveything out with a can of compressed air. If everything is fine there than I would look at getting an good aftermarket cooler.

you better refer to the tecnician for that coz u ned to recon your cpu and heat sink....becoz i think it is notin a proper posistion ryt now"