Perhaps if you read ALL the words next time...
I am running Microsoft Outlook on my Windows 7 computer without incident. I have never heard of anyone with any problems doing this.
I believe what may have been referenced is the fact that Windows 7 does not come with Outlook Express pre-loaded any more, unlike previous versions of Windows. I believe that you can still download Outlook Express from somewhere on the Microsoft web site and run it on W7.
The real issue is that Windows 7 is a 64 bit system. Office 2003 is 32 bit.