Unless you're talking Windows 98 and earlier, Fullscreen Mode does not give "full access" to your computer's resources. Yes, it used to; nowadays it basically minimizes other claims on resources through prioritization of Windows event handling. You can accomplish pretty much the same thing by setting the process priority to HIGH.

In the "old days" when we coded primarily with the Win32 library, we had to write a lot of code under Fullscreen Mode to provide the functionality normally provided by Windows since applications couldn't operate without that code. Nowadays, that functionality is provided whether you want it or not... Run a resource monitor in the background sometime when you're playing the game (if you have one) and you'll see what I mean.

As a "for instance", the Win32 library provided macros to handle all the various OS events (e.g., mouse clicks) that came in raw form to a Fullscreen Mode application. In Windowed mode, those events came to the application already "translated". In Fullscreen Mode, we discarded those OS events we weren't interested in (although we still had to reply to the OS that we'd received them); in Windowed mode, events were discarded automatically...

That "translation" had a lot of overhead associated with it; Fullscreen Mode applications could be significantly smaller in executable size and faster in execution speed. Windowed mode applications required less code to be written.

That's really no longer the case. As the OS has matured (and Microsoft has added a whole series of new bugs and quirks), the coding environment has changed. So, run ESO however you like...

RE: Aero... if you have up-to-date drivers, you should be getting no complaints from Aero. Check your settings for Aero and the date on your graphic drivers. The problems with Aero have been -- at least to the best of my knowledge -- resolved. Aero is a memory pig and a processor hog, but so is everything else under Windows...