User uses GMDR.Load's Update function to download an updated .exe (GMDR.Load .exe) from the update website; at the end of the download process the user gets a Windows error message "Access Denied" with no further information.
GMDR.Load, after completing the download of the update .exe, saves that file to disk, and tries to leave the filename of that update in the system registry. To make the update available to any/all user accounts on the machine, GMDR.Load tries to write that information to the "Current Machine" part of the registry (instead of that part specific to the current user, and only visible to the current user account, "Current User"). Vista regards the Current Machine part of the registry as more sensitive than the user specific area. If the Vista security level is above a critical level (which appears to vary widely with different Vista versions), Vista blocks that access/write. [Of Note: GMDR has never been able to reproduce this problem on any of their Vista test machines - independent of security settings and/or version... go figure.]
When the user wishes to download an updated GMDR.Load .exe, they need to do so while having "administrator privileges".
The user nominally uses a desktop icon, double clicks on it to run GMDR.Load. If the user instead of (left) double clicking the icon, right clicks it - they will be presented with pop-up where "Open as Administrator" is one of the choices. By clicking that, and clicking to allow execution on the next screen, GMDR.Load will be invoked with temporary Administrator privileges. If the user then invokes the GMDR.Load Update function and selects "Update GMDR.Load" it should run as before on XP or earlier Windows. After downloading the update, GMDR.Load leaves an icon on the desktop. If the user then uses the right click "Open as Administrator" function to invoke the update, it should install cleanly. After that (unless further program updates are sought), all subsequent invocations to GMDR.Load should be through the nominal / standard double-clicking its icon.
Special thanks to Rick Martin for generating the workaround.