Heavy games keep crashing

[RoiMan]

Almost all the heavy-graphics games crash. I have a new computer -

i7-3770 3.5Ghz proccesor,
650 GTX Ti graphics card,
16 Gigs of memory,
Asus P8Z77-M motherboard

after even 5 minutes, the following message appears-

"........ has stopped working.
Windows 7 is looking for a solution.."

then closes.
Please help?

 

[landerio]

What has stopped working? Your new computer is a brand or DIY?

 

[RoiMan]

What has stopped working? Your new computer is a brand or DIY?

...... Is representing the game. If it's battlefield 3, if its GTA IV..
We have bought all the parts seperately, one's an MSI the memory is Kingston
so I quess the whole computer isn't a brand?