I'm guessing that you probably need that there if you want your scanner to work.  Here's a little description on what it is:

Still Image Monitor (Stimon.exe) is a tool that is installed by Windows Millennium Edition (Me) and Windows 98 when a Universal Serial Bus (USB) scanning device is successfully enumerated. Stimon.exe is configured to start automatically during the Windows startup process, and is loaded from the following registry key:

HKEY_Local_Machine\Software\Microsoft\Windows\Current Version\Run

Stimon.exe enables a USB still-image device (such as a scanner) to initiate data transfer to a program. This is called "push model" behavior. For example, if your scanning device has a Scan button, it may start a program and begin scanning when you press it.

Stimon contains two modules: Event Monitor and Control Center.

-  Event Monitor detects events from connected USB scanning devices.
-  Control Center determines how to react to these incoming events.