Hi John,
You need to check the drivers and software that were installed with the scanner. Make sure that the drivers are XP compatible and that the scanning software that is trying to run at startup is either XP compatible or that you're able to run it in a different version of Windows (i.e. 98) Compatibility mode.
This may be able to be done without totally uninstalling all of the software, but it does sound like a driver version problem more than software (or "program"). If there are nodrivers listed for XP, try the 2000 drivers. Do a full un-install and then a custom install just installing the drivers and not the software.
Check the manufacturer's site for XP FAQ's as well as the MS XP site for hardware compatibility.
Please post a comment with what you have tried and have not tried. Also check out this site for a list of what services that XP runs at startup, and which ones are essential:
http://www.blkviper.com/WinXP/servicecfg.htm
(remove any spaces from the URL)
HTH