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 (http://www.intel.com). 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.