There is really only two ways:
1) Hand edit the registry (ick, you don't want to do this)
2) Use the Win32 Services API to remove it.
#2 is what all programs and things like instsrvc.exe use and is
the only supported method.
I don't know the legality of making instsrv.exe available, but I
found it fairly easily using Alta Vista at:
Dale E. Reed Jr. Emerald and RadiusNT__________________________________________IEA Software, Inc. www.iea-software.com
For more information about this list (including removal) go to:http://www.iea-software.com/support/maillists/liststart