How to check if 32 or 62 bit Operating System is installed in the pc

For XP pc :
1) Click Start > Run

2) Type msinfo32 and click Ok(We can also type winmsd.exe and click Ok)

3) A System Information window opens

4) In this window, if the 'System Type' and 'Processor' information is listed as x86 Family, then the computer is running a 32-bit version of the Windows operating system.If the 'System Type' and 'Processor' information is listed as ia64 or AMD64, the computer is running a 64-bit version of the Windows operating system.

Or

1. Click Start > Run, type sysdm.cpl, and then click OK.

2. Click the General tab. The operating system appears as follows:

3. For a 64-bit version operating system: Microsoft Windows XP Professional x64 Edition Version <> appears under System.

4. For a 32-bit version operating system: Microsoft Windows XP Professional Version<> appears under System.
Note : is a placeholder for a year.

For Vista pc :

1) Click Start > Rightlclick on 'Computer' and choose Properties

2) In the information window that opens, 'System Type' will show the operating system as a 32bit or a 64bit
or
1. Click Start > In Start Search, type msinfo32 and press Enter key

2. System Information window will open

3. In this 'System Type' will be listed as x86 or ia64