Hello, I currently own the following Intel system,

Operating System System Model
Windows 7 Ultimate Service Pack 1 (build 7601)
Install Language: English (United States)
System Locale: English (United States)

Enclosure Type: Desktop

Processor a
3.07 gigahertz Intel Core i3 540
32 kilobyte primary memory cache
512 kilobyte secondary memory cache
4096 kilobyte tertiary memory cache
64-bit ready
Multi-core (2 total)
Hyper-threaded (4 total)

Main Circuit Board b
Board: Intel Corporation DH55PJ AAE93812-302
Serial Number: BTPJ10800DUH
Bus Clock: 533 megahertz
BIOS: Intel Corp. TCIBX10H.86A.0037.2010.0614.1712 06/14/2010

I want to know that how can I change the BIOS from 32bit to 64bit. Also I have installed Windows 7 Ultimate 32bit, can I install Windows 7 Ultimate 64bit over it without effecting the programmes that I have installed on my system.

You should not change the Bios to 64-bit. Usually it is your operating system that is either 64-bit or 32-bit... given that your processor supports 64-bit, which yours does. You should just be able to install Windows 7 64-bit... however, you cannot go from 32-bit to 64-bit without being forced to do a full install.

If you decide to switch to 64-bit, you will need to backup everything that you want to keep. And then once you are done, you will have to re-install all of your programs/games/ect.

The latest BIOS for the DH55PJ board is version 0046 available from the download center in the support section of Intel's website. The release notes describe changes and fixes since your 0037 version. Decide if any warrant a BIOS upgrade. 64-bit Win7 drivers for motherboard devices are available from the download center too.