How to determine if you have Windows 7/Vista/XP 32-bit or 64-bit edition
To find out if you are running the 32-bit or 64-bit edition of the Windows XP, Vista or 7 operating system:
On Windows Vista / 7
1. Click Start → Computer.
2. From the menu bar, click System properties to view basic information about your computer.
3. Under System → System type you will find system type details.
On Windows XP
1. Right-click My Computer, and then click Properties.
2. In the System Properties dialog box, click the General tab.
3. Under Computer you will find system type details.
If you have the 64-bit edition, text '64-bit Edition' will appear at the end of your operating system. If you do not get this text, your computer is running the 32-bit edition.
For more information, please see microsoft.com.