PC wont startup!!!

hi!! every one.. this is ayan.

My PC config is:
cpu: Intel Quad core 2.83ghz
os: win 7 ultimate x64
ram: 4 gb ddr3
hdd: 1 tb wd(black) & 500 gb seagate
gpu: Nvidia 9800GT 512 mb

Now the problem..
My pc wont start up..
it started not so long ago.. i updated my nvidia driver.. to 258.96(some thing like this) since then i've been facing this problem..
when my pc boots up it shows the version of GPU.. where is mentions copyright 1986-2008, its replaced with copyright 19 followed by some funny symbols...
then it shows up boot menu.. there i select my os n it shows starting windows and then woooshhh.... a halt... nothing happens then... i restarted it.. same...
then opened up my cabinet n took out the gpu n ram, cleaned them n then again placed it back..
tried it.. but again failed... i left it for some days.. then i started it.. it worked for 2 days.. then yesterday.. it was the same...

can anyone help me out...

i tried at other forum too.. WIndows seven forum..
Windows not starting!!! - Windows 7 Forums
this is the link to my posts there...