Thanks Sergey, I found out what is exactly causing it:

If you have both VFP9HTML and VFP8HTML merge modules in a setup project they don't get along and the VFP9 registry keys will not be installed from the module. If I don't include VFP8's HTML, the setup compiles (with VFP9HTML merge) with no problems. Same with just the VFP8HTML merge. The workaround was to shift to Visual Studio 2005's setup project and include the VFP9 HTML Help registry keys manually. Installsheild just won't do it.

Richard

>>I keep getting the following error message from Installsheild (the one that came with VFP9) during the build:
>>
>>ISEXP : fatal error -6058: Error merging Microsoft Visual FoxPro 9 HTML Help Support Librar with module ID C:\Program Files\Common Files\Merge Modules\VFP9HTMLHelp.msm
>>
>>Everything looks in order. I've started this Install project from scratch due to corruption from the last one.
>>
>>Any ideas?
>>
>
>Richard,
>
>Check http://support.installshield.com/kb/view.asp?articleid=Q109523