To find out if you have a 32 bit or a 64 bit operating system, follow these steps:
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In Windows XP: - Click Start. 
- Locate My Computer on the Start menu. 
- Right-click My Computer and select Properties. 
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If you see x64 Edition listed under System, you are running the 64 bit version of Windows XP. If you do not see x64 Edition listed, you are running a 32 bit version of Windows XP. 
 
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In Windows Vista and Windows 7: - Click Start. 
- Locate Computer on the Start menu. 
- Right-click Computer and select Properties. 
- Look under System in order to check the information about your system. 
 
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In Windows 8: - From the Windows Start screen, locate Computer (for example, you can start typing "Computer" directly in the Start screen) and then right-click its icon. 
- Select Properties in the bottom menu. 
- Look under System to see the system type.