4GB ram and 64-bit , 2.13 GHz processor.

i always have this laptop crashed. almost twice a day. 

this mostly  happens when i watch online videos (for a length of time say more than 20 mins, be it netflix or youtube). watching DVDs are OK. 

Also if i run some code/program that needs quite a bit of computer resources, it crashes and gives out colored screen.

color widely varies.

any suggestions?