Difference between a 32bit computer and 64 bit computer

The terms 32-bit(x86) and 64-bit(x64) refer to the way a computer's processor (also called a CPU), handles information. The 64-bit version of Windows handles large amounts of random access memory (RAM) more effectively than a 32-bit system.




The main difference between a 32 bit and 64 is that 32 bit system has 4gb(gigabytes) of space for addressing means that the 32 bit system has a limit of 4GB RAM to process data where as the 64 bit operating system has 2^64 bits of space to address and supports 16 hexabytes of RAM to process data. 

How to find out which version iam using?

select computer from desktop >>righclick properties>>

or

Open System by clicking the Start button , clicking Control Panel, clicking System and Maintenance, and then clicking System.

Under System, you can view the system type.

What are the Limitation of 32bit system?

32 Bit has limitations. The first and largest Limitation is the 4GB limit. Meaning that 32 Bit can not and will not recognize or utilize 4GB of RAM. The Max you will get is 3.5GB of RAM recognized and utilized on a 32 Bit system. No before anyone goes off on me for the fact that Vista SP1 will show that you have 4GB installed you still do not get to utilize that 4GB as it will not use that other 512MB.