Alienware 14x crashing when GPU stressed (even in 0% load) Pls Help me

i bought alienware m14x r1 with 1.5GB nVIDIA geforce GTX 550 GPU. i behaved quit well with out any hiccups.      in november i installed Windows 8 64 bit in my machine with lots of my working softwares like 3ds max, photoshop, modo, solidworks. but not a single game was installed. due to huge work load my device remain turned on for around 20Hrs daily. but not stressed in any department of  GPU & CPU. just work on softwares like photoshop.

in December  i faced the first problem when i working in one 3d model, Gpu suddenly wake up with its full speed & then after 2 minutes of this the whole device shut downed. Even power button fail to wake it up. After hour of rest it able to turned on again.  i thought i may be 3ds max 2012 problem so not take notice about this sudden death.

but day day after day it keeps happening, next it shut down the device when working in Modo software. Even the NFS most wanted 2012 is not running well in my device after 30 seconds play all graphics goes crazy then sudden death.now i'm unable to work nor play.

i tried to figure out the problem so installed furmark GPU test . it started with idle temp  72 0c & within 1minute of stress temp reaches 930 c, also fan remain in 0%. 

next i installed nVidia ntune tool to tune my Gpu's Fan cooling system but when ever running nVidia  monitor tool system crashes with a big blue screen .

i don't know what  going wrong or what happened to my device & how to solve this. if anybody tell me how to fix this issue i will be remain helpful to him/her.   

Thank you