Rolling back a Windows 2000 Service Pack

I have a little problem I am hoping someone may be able to share some light on. I have 4 Windows 2000 pc’s 3 with Service Pack 3 and 1 with Service Pack 4. Unfortunately when the SP was applied the archive feature was NOT checked therefore when you go to add remove programs the SP is not listed. Is there an easy way to roll back a service pack? I need to do this roll-back because the SP3 and 4 are affecting a program that we use and unfortunately the Software creator has no fix for the problem.
Thanks in advance.