Running XP SP2. Outlook 2000 SP3. IE7

I have Outlook 2000 installed on my PC and want to (once again) have
it as my default e-mail for Internet Explorer7.

My problem began after I launched Microsoft Outlook 2003, today.
Thought I might try the trial offer to compare '03 against '00 .

Therefore, after selecting Outlook 2003, "Microsoft Office 2003 Set
Up" launched. The window asked for my product key. I entered the
"Key" number from my Office 2000, software.

I Immediately received an error message stating that I did not have a valid
number. I selected
the cancel button and closed the window.

Now each time I open my browser click on the mail icon - "Microsoft
Office Set Up 2003" launches.

What steps do I take to stop "Office Set Up 2003" from launching?
I want my browser to revert back to selecting: Outlook 2000 as my default
for e-mail.

I have already tried: ToolsInternet OptionsPrograms and Selected:
Microsoft
Outlook. Unfortunately, after selecting the "apply" button and clicking
"ok"-"Microsoft Office Set Up 2003" still launches.

I also went to the add/remove program selected "uninstall "Office 2003",
the program uninstalled "Office 2000".

Fortunately, I have Norton Go Back and simply restored.

An important part of the problem I will reiterate is: Office Set Up 2003
only launches when I access e-mail from my browser, IE7.

When I click on the desktop shortcut for Microsoft Office 2000 opens just
fine.

Thanks for any suggestions.