Un installing spk6a

I have an application that will not run on service pack 6, yest the laptop I am working with has spk6a. The user did not mark the check box to backup previous files in the event you want to un-install the service pack. Is there a way to modify a config, ini, or log file to fool NT or the app into thinking service pack 5 is installed? I don’t wan’t to run a repair because then it will write over some drivers that I do not have the software for. Thanks.