After updating the software Mac won't Start!!! Plz help.

Hi last week I brought MacBook Pro 17" Lion 10.7.3, 2.4 ghz Intel core i7, 4gb Ram.

I updated its software before going for work in countryside. But now when I restart it stops on grey screen with apple logo after the blue screen.

I can mov the cursor but I login window doesn't comes up...

I didn't brought my Back up Drive to boot with....

I went through the discussions on my iphone and have tried doing all this ..

1. Went into safe mode and into disk utility and have verified disk and repaired disk.

Have also done verifying and repairing disk permissions. It goes all good but still when I restart it gets

Stuck on that grey screen with no login space.

2. Have also tried going into single user mode and tried doing those steps about Fsck

But only first time it says file modified and after that I tried it again and everytime it says disk is ok.

And then restarted it but again gets stuck.

3. Have also tried going into terminal in utilities and putting the commands that Kappy has tried to explain to someone through sudo chow.

And restart it but then also gets stuck on grey screen.

4. I tried locating /System/Library for editing the start up items but can't find that.

I will go back to main city in 2 weeks. Till then I can only start in safe mode. Any suggestion plz.