Since the release of Microsoft Dynamics GP v10.0 I have seen this question asked many times over on the various newsgroups I monitor (see the Newsgroups Links on the left hand panel of the blog).
The quick answer is.... it has moved into the Data subfolder.
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OK, I am just kidding, how can I end the post without an explanation?
This change was made to keep Microsoft Windows Vista and its User Access Control (UAC) protection happy. One of the major benefits of Vista is UAC*, which is designed to prevent rogue applications (viruses, worms, trojans, etc.) from getting a foothold in your system. It does this by asking for elevated Administrator status when any action is trying to change the registry or system files. It prevents internet applications from getting out temporary folders with Internet Explorer protected mode, thus preventing malware installing itself. It also prevents applications writing to the C:\Program Files folders.
Because Microsoft Dynamics GP needs read/write access to the DEX.INI as well as read/write access to the custom forms and reports dictionaries, all these files have been moved into a Data subfolder which is created during the installation with adjust permissions to allow read/write access even if UAC is on.
* Before you complain that UAC breaks applications.... Applications that have been updated for Vista compatibility understand the new security guidelines and work fine. Old applications written before Vista might have issues and need to be set to Run as Administrator.