Windows 7 shuts down when i press restart

The function of the button can be reset to a different function.
check in the windows 7 power profile settings...
You can set it to shut down or restart...
Download the entire manual from the manufacturer's website.
(the full manual does not come with the unit)
The manual may show how to set it.
Also, in your bios settings, there may be a setting for that function.

Thanks for the suggestion. I am currently looking into BIOS. But I think I need to clear out that I am trying to restart through the START Menu (through 'windows 7 Shutdown tab' with the options given 'Log Off' 'Lock' 'Restart' 'Sleep'). Its when I choose 'Restart' from there my PC shuts down, it doesnt restart.

btw, PC has just one power on button in the casing. No additional restart button there.

I just went through BIOS. My BIOS version is 'American Megatrends Inc. BIOS P01-A3 dated 12/31/2009. And when I went through Power Settings, I found ACPI Suspend mode which has two options 'S1(POS)' and 'S3(STR). It was S3 by default so I changed it back to S1. Also there was something called 'Deep Power Off Mode' I disabled that too.

And to my surprise, after I hit 'Save & Exit' from BIOS. Pc doesnt reboot. I have to manually shut it down from the power button.

After changing these from the BIOS also, the problem is not solved.

Any further suggestions?

Thanks in advance