I know it's been said before but I'll say it again, DON'T install to the default directory.
I'll repeat that, DO NOT install to the default directory (C:\Program Files (x86)\ ...
Windows 7 (any bit), Windows Vista (any bit), Windows XP (64 bit), etc ...
These are designed with security measures. If you install a program like this one (SHIII with all the mods), you cannot get it to run because the mods and patches and such are designed to update files in the game directory. If you are using the "Program Files (x86)" directory, these security measure in the Windows OS's are designed to block the files from being edited and manipulated by the mods from SHIII and thus, the game will not run. If you only want to run vanilla SHIII (without any mods, updates, patches, and a generic resolution), then by all means, use the "C:\Program Files (x86)\ ... default installation.
Best suggestion is to create a custom folder for your install of SHIII.
I use "C:\Program Games\ ..." . This way Windows does not automatically block any files from being edited and manipulated by the mods and patches I put in it.
I believe a lot of the errors people are posting are because of the 'security measures' put in place by Microsoft on these newer OS's.
And another think regarding resolutions for those with the larger screens and best video cards; there are mods here in the forum for high resolution screens. See this one for a great example
http://www.subsim.com/radioroom/showthread.php?t=196400
The third post from Brett25 will give you an excellent place to start for getting the game to run on a high resolution. You will have to search around for all the mods to get everything looking proper on the screen, but it's worth it.
Frau Kaleun mentioned earlier and it's worth mentioning again, take your time and go one step at a time. Make sure the vanilla is working properly first before you start putting updates and patches, mods and customizations to it all. Otherwise, you spend twice as much time and still have to go step by step.
Good luck to you all.