You have probably just lost the icon and not the actual code.
First, check to see it is not on one of the program menus. Check it is not in the recycle bin.
If it is not do as follows:
Double click on the My Computer icon (or open My Computer)
Double click on the icon for your C drive.
Double click on the folder for Program Files (you may get a warning but just carry on)
Double click on the folder for Outlook Express
Within there you will have an icon for msimn.exe (an envelope)
Hold the mouse cursor over the msimn.exe icon the hold down the RIGHT mouse buton.
Drag it to your desktop and let go.
You get a small menu and one of the options is Create Shortcut Here.
Select that and it should put an icon on your desktop.
Double click on it and Outlook should start..
You may find it is already configured.