Inspiron 15R freeze

I have just bought my Inspiron 5010 few months ago and it keep freezing recently.

It can freeze at any time, when I surfing the net, at the windows login page, even freeze at "starting windows" .

The screen freeze and the light for CPU does not turn on any more. It shows no respond even waiting for a few minutes.

 I have to press and hold the power button to turn off the laptop.

Sometimes  when I turn on the laptop, only light for power is on and the screen shows nothing,

I try  few more times, It becomes normal again (but still have the chance to freeze)

Anyone can help me? Thanks!

Intel® CoreTM i5 460M (2.8GHz/3MB cache)

 4GB Dual Channel DDR3 SDRAM at 1333MHz

320GB hard drive (5400RPM)

Dell Wireless DW1501, 802.11 g/n 1x1 Half Mini Card

Windows® 7 Home Premium 64-Bit