(click the picture to enlarge)
Windows 7/Vista :
1. click start
2. Right click on computer and select properties.
3. A windows will appear. In the picture below you can see the operating system is 64-bit. it will state 32-bit operating system is your operating system is 32-bit.
|This snapshot is taken from my desktop properties|
1. Click start - right click on MY COMPUTER select PROPERTIES.
2. A window will open. Under the system you will see the operating system 32-bit or 64-bit.