Problem: http://support.apple.com/kb/TS2377

Welcome to Apple Communities

Take it to an Apple Store because your graphic has got failures

• MacBook Pro 15-inch and 17-inch models with NVIDIA GeForce 8600M GT graphics processors
  • MacBook Pro (17-Inch, 2.4GHz)
  • MacBook Pro (15-Inch, 2.4/2.2GHz)
  • MacBook Pro (Early 2008)
• These computers were manufactured between approximately May 2007 and September 2008

You might be out of luck - did you purchase your computer less than 4 years ago? If so, Apple will replace the logic board (and affected GPU) free. If it's been over 4 years, then you may be too late. Take it into your local Apple Store and see if you qualify for the free fix.

Good luck,

Clinton

You could also beg and plead temporary insanity for four years... I doubt that it will help, though. See how much they'll charge for a new logic board - it's bound to be cheaper than buying a new computer.

Best luck,

Clinton

The MacBook Pro has got hardware soldered to the logic board, so the problem is that not only the logic board will be replaced

No. Repair it or buy another one