My laptop has suddenly frozen, i turned it off by the power button and whenever i try to turn it on it turns white screen, then shutsoff after 3-5minutes.

If the above doesn't help, you need to have the logic board replaced by Apple. Been there, done that, and it's not too expensive.

Resolution

1. Disconnect any devices connected to the computer including printers, hubs, and third-party keyboards or mice, and test the computer again by trying to turn it on.
2. If you're using a MacBook or MacBook Pro, check the battery level. Press the small button on the battery or on the side of the computer. You should see lights indicating the battery's level of charge. If you see just one light blinking, the battery needs to be recharged. Use the computer with the adapter connected to recharge the battery.
3. Unplug the power adapter from the electrical outlet and from the MacBook, MacBook Air, or MacBook Pro. Wait one minute. Plug it back into the wall first, then to the computer. Make sure the electrical outlet is working by plugging in another device (such as a lamp). When you plug the adapter back into the computer, the power adapter LEDs should light up green or amber.
4. Inspect the MagSafe port on the computer for debris, such as metal stuck to the magnet in the port, which might prevent the connector from seating properly. On the adapter side, look at the DC connector for dust or other debris and check whether pins are missing, bent, or stuck down. If you find any of these to be true, see Apple Portables: Troubleshooting MagSafe adapters for instructions on cleaning the adapter.
5. Make sure you are using the adapter that was designed for your computer. If you aren't sure or if you need a new adapter, learn which adapter is appropriate for your computer.
6. Press the control key, the command key, and the power button simultaneously and hold for three seconds to try to restart the computer.
7. Reset the PRAM. After pressing the power button, hold down these keys simultaneously: Command-Option-P-R, until you hear the startup chime at least one additional time after the initial startup chime.
8. Reset the SMC for the MacBook And MacBook Pro by removing the AC power, removing the battery and then holding down the power button for five seconds. On the MacBook Air, press (left) Shift-Control-Option along with the power button once. Note: You must use the keys on the left side of the MacBook Air keyboard.
9. If you recently installed additional memory, make sure it is correctly installed and is compatible with your computer. Remove the new memory to see if the computer starts up properly without it.

Also:
The MacBook SMC Firmware Update v1.1 improves the MacBook's internal monitoring system and addresses issues with unexpected shutdowns. This update is recommended for all MacBook systems, including those that received warranty repair.
You can use the Software Update feature of System Preferences, or download the MacBook SMC Firmware Update v1.1 from Apple Software Downloads.
Note: If your MacBook is running Mac OS X 10.4.6, you won't be able to see the SMC Update until you update to Mac OS X 10.4.8. Once you have updated your system software, the SMC Update will appear as an option in Software Updates.
MacBooks running Mac OS X 10.4.7 will be able to download and install the SMC Update, so it is not essential that you update your system software, although Apple always recommends updating to the latest version of the system software.
If your MacBook is in a state where it will not remain on long enough to install the update, wait for the issue to reproduce itself. Once the MacBook has turned itself off, turn the computer on by holding the power button down. Keep the button down until you hear a single long tone. Once you hear the tone you can release the button, install the recommended updates, and restart normally.