I would try to get it running on the Vista system since the other OS seems to have problems all of its own.
I would do the following:
Make sure your user account is an Administrator account. (Control Panel, User Accounts)
If you have it installed on the Vista system, uninstall it and delete any Divine Divinity directories / files under C:\Program Files (xx)\GOG.com\
Create a directory outside of Program Files ( I use C:\Games)
Turn UAC OFF prior to the fresh install. (See attached image)
Right click the setup.exe and click "Run as an administrator" in the resulting dialog.
On the first dialog of the GOG installer, click the Options button in the lower left corner and direct the install to the C:\Games directory. Install.
If you are still getting the "Unable to execute" error, disconnect from the internet and disable your firewall as that is usually the offending program once UAC is turned off. Turn UAC and your firewall back on once the install is complete. ( Also installing outside of Program Files helps eliminate some install errors)
After the install, right click the game shortcut, click Properties, click the Compatibility tab and check mark the "Run this program as an administrator" box.
I would try the game without a compatibility, if you have problems try the newest compatibility mode first working your way from newest to oldest till you get a stable game.
It is important that you have the latest video drivers as DD does not work well with the older versions.
Click here for ATI Click here for Nvidia The steps above have given me stable, playable installs on both Vista 64 and Win 7 64.
If you have a dual / quad core CPU you can also try the following.
If you have static problems there is a program I use to set the affinity to a single core on multicore systems. It is not necessary but helps on SOME systems to do this. You can set it manually first, if that does not help there is no need in using RunFirst
To set it manually, start the game, ALT-TAB out of the game, open task manager (CTRL - ALT - DEL ), find the div.exe on the Processes tab, right click the div.exe name and click Set affinity . . . on the resulting dialog. Un-check all but the CPU 0 check box. (See attached image) Close the task manager and play the game. If this helps I suggest using
RunFirst as it sets the affinity for the game without having to go thru the task manager process each time you play.
If you have a dual core AMD CPU you may also get some benefit from the
AMD Dual Core Optimizer. This helps some games on systems with the AMD CPU.
Hope this helps . . . =)