check the credentials under the mcshield service.
you can log the install if you need, putting voicewarmup in the reg, you can find the doc on nai site by searching on voicewarmup.
Delete all temp files, start run %temp% ok delete all
check winnt\installer and right click and check the summary for all files, if they are network associates delete them
put the install files into %temp% and run the msi file to install.
I also assume you deleted the legacy keys from the reg, this is in the doc you had tried.
the install uses microsoft installer, sometime you have to repair, or upgrade this from microsoft.
gl
FatesWebb
if you do what I suggested it is not my fault...