It sounds like you had an Alpha version of SDP 6.6 installed previously, and it has not been uninstalled correctly.
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If the uninstaller doesn't fully remove all the components, do the following:

    Delete the folder where you installed QNX SDP.
    Delete the "QNX Momentics" desktop shortcut and the link in the Start menu.
    Find and delete all occurrences of .com.zerog.registry.xml. This is a hidden file, so you must enable the Show 
hidden files and folders option.
    Delete the QNX SDP entries from the Add/Remove Program list by choosing Control Panel > Programs and Features from 
the Start menu, right-clicking on each QNX SDP entry, and then choosing Delete from the list.
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Hope this helps.

Natalia

> On our project we are upgrading form 6.5.0 to 6.6 of the QNX SDP. When I run 
> the 6.6 installer I get the initial Welcome dialog and I click Next at the 
> bottom right. After that I get a popup dialog saying "QNX Software Development
>  Platform 6.6 is already installed in the following location: NULL". I tried 
> uninstalling all QNX related programs and have rebooted several times but the 
> popup persists.