this happens without my intervention with the keyboard. In fact I am not near it. This alt tabbing mainly happens after the opening movie to each game just before the gameplay sequence, usually during a "cut scene" but sometimes during the opening movie interrupting it and crashing entirely, other times it is the game play when you're given control at times I can alt-tab back into the game, and in that case, play for quite a while. However, more often than not it alt-tabs out and crashes completely to the desktop just after the opening movie or during it. In this case, it briefly shows the minimized window "Icon" on the lower left hand side of the task bar before fading out and closing(without my intervention).
the only thing I can point out is I HAD McAfee on my system(via AT&T ISP download) I hated the thing so I removed it via "McAfee removal tool" and also used Revo uninstaller command "force uninstall" to rip out the rest of McAfee residue. some people on google had suggested it was McAfee, but I removed McAfee and this happens with other games too. I have no instance of McAfee Security Suite, or AV on my system and the alt-tabbing still occurs in this game and also in other games made close to the time period these games were made.
I have attempted other keyboards, various wired and wireless varieties still the same result, though some seem to crash it out right more often(but randomly) others allow me to alt-tab back into the game. B.M 1, 2 and 3 alt-tab out automatically usually during or after a movie, this has occured with any game made during the time period when these 3 games were made utilizing opening movies,, I will point out that these B.M. game's movies and gameplay were set to play at the same resolution as the game and in the case of Black Mirror 1, the same refresh rate and graphic mode on both movie play and game play screens.(accessed during settings feature) I do not keep my hands near input devices when watching movies. I usually sit back to watch.
Using a Dell Optiplex 780
Dell ATI Radeon Hd 3450 Dms-59 256mb Y103d Pcie X16 S-video Graphics Card B629(using catalyst legacy 3.9 for windows vista/7 this is the latest for this particular card)
Windows 7 Professional

Your description sounds a bit weird because you're talking about ALT+TABBING but refering to minimizing, maximizing or switching tasks. A task can be any piece of software running on your system (games, tools, etc.). ALT+TAB is just one key combination that enables the user to minimize, maximize or switch tasks. Programs and Windows don't emulate this key combination to achieve the same. They have their own commands to do it. So no need to have a suspicious look at your keyboard. ;)

So the real question is: Why does your system minimize games of a certain era?

And that is really hard to say. It's not a common behaviour but there are countless possible reasons for it.

The first reason that comes to my mind is that there's a tool installed that is monitoring your system and displays a message in case of certain events. And to display this message it minimizes other tasks (the games in your case). For example: I used a firewall that displayed a message when a program accesses the internet. To do this it minimized all tasks so that I could read the message and cancel the access. And that's just one example. Other tools display messages, if you get an email, a chat message, when the color scheme changes, the video chip temperature exceeds a certain temperature. There are countless examples.

So an idea would be to have a look if always happens something at the same time when a game gets minimized. Sometimes its hard to notice because some messages have already vanishes when the task is finally successful minimized (depending on the system it can take a few seconds). If a game offers a window mode you should use it, because you can see what happens in the background when the game gets minimized.

Black Mirror 1 doesn't have a window mode. Black Mirror 2 & 3 do have a window mode but you can't activate it from within the game. You have to enable it manually. Go to your "Documents" folder and enter the subfolder "BlackMirror2" (or "BlackMirrorIII"). Open the file "config.xml" with the Wordpad (not with Word). Change the following values:
Fullscreen="1" to Fullscreen="0"
Width="1920" to Width="1280"
Height="1080" to Height="720"
Window="0" to Window="1"
The old Width/Height value depends on your system of course. The Window line does not exist with Black Mirror III and isn't needed there.

If you are able to spot down the tool that's causing the task minimizations you should either deactivate the feature (for example displaying certain messages) or uninstall the tool.

If you are unable to spot it down I suggest you deactivate/uninstall as many tools running in the background as possible. If the games run stable now then activate/install them again step by step to spot down the tool causing this problem.