How to find whether a operating system is 32 bit or 64 bit

I had to install one hotfix from microsoft, while downloading i was given different options to downlaod the correct package related to my Operation System. I was using the windows server 2003 operating system.
To find the information in windows server 2003,

• Click on the MyComputer --->Properties --> General Tab.
• If the System Name is specified as "Microsoft Windows Server 2003 Enterprise Edition" then it is 32 bit OS.
• If the System Name is specified as "Microsoft Windows Server 2003 Enterprise x64 Edition" then its 64 bit OS.

Update: I found that there is also a very good article available from Microsoft to find the information for other OS as well. (http://support.microsoft.com/kb/827218)