Computer Drops FPS after closing games

Recently I installed an MSI Gaming Z170A m3 motherboard and i7-6700k processor, operating on a brand new copy of Windows 7 (all updates installed). While I am playing any game of any intensity, It runs well at 60 fps at almost all times. However, when I close these games after playing any amount of time, my windows and everything in them goes to unusable FPS. The only thing not affected is my cursor. When I relaunch the game, and play it, the FPS is just fine, only for the game. My CPU Temps are also normal while running the games. While the games are off and the fps is low, the CPU and ram consumption are low.

So far, I have tried

• completely wiping out my Nvidia drivers and reinstalling them with a clean install. However the problem still occurs
• Doing a power cycle (turning the PC off and back on) makes my computer operate at normal FPS.
• Ending dwm.exe in the task manager also makes it so I can operate my windows at normal speeds as well (even when it relaunches its self).

they said switching from aero to basic won't turn off dwm.exe (but if you disable dwm.exe in the service list you'll be switched to basic mode).
dwm.exe works because all of the individual programs write their visual contents to memory & then dwm.exe creates a single composite window from the information in memory.
i would try to disable features of aero one by one & see if the problem goes away - and if not, try switching to basic mode to see if the problem goes away.
if none of that works, i'd try disabling it before going into a game & then reenable it after coming out of the game to see if that makes the problem go away.

but technically, that workaround isn't a fix.
seems the problem is either the version of drivers you are using, or the operating system.
hard to think it is each individual game you play with the same problem, unless you are using some other program in combination with each game that could be causing it.
if you aren't using a program in combination with the game, you could always try one of the scans to check and repair|replace any broken operating system files to see if that helps.
otherwise i'd simply reinstall the operating system, because if it comes back again immediately after the reinstallation then it sounds as if microsoft has a bug in their software that needs to be fixed with an update.

there's also the direct x diagnostic tool, but i don't know if your problem would be tested for in the list of tests.

doesn't seem likely to be a hardware problem, because the operating system would give the graphics card some sort of flag to set the graphics card into 3d mode where the clocks are raised to higher speeds for an improvement in performance (they lower speed for 2d performance because it reduces power consumption).
you said you can end the dwm.exe process in task manager, and when it re-enables itself the problem isn't there.
that tells me there is a flag being seen by the graphics card & the only way to create the problem from there is if you or somebody else has managed to get into the inner workings of the graphics card & there is a second flag of different detail being sent to the graphics card after leaving the video game that isn't being registered by the graphics card - thus only one of two flags are registering/known.

to say the least, it is a software problem & the only way to fix it is to find out which software is the cause of the problem.

if you aren't seeing anything in the event viewer of the operating system that suggests a reason for it to be happening (and it would show up every single time you exited a video game), then there isn't really a chance to use some user-friendly software to see the code's execution to determine precisely where the problem is coming from.

with that said,
if it is the drivers, use a driver uninstaller to totally wipe out the installation (because simply doing it from the control panel leaves things behind that could cause a conflict (or even the same exact thing to happen technically) with the new installation.)

if it is the operating system & the scan to repair|replace broken or missing files doesn't fix it - then a reinstallation from a fully working disc should fix it (i say fully working, because what if the file is broken on a copied disc? then it would happen every time you reinstall fresh.).

i'm a little curious, how do you know your frames per second are low?
i've opened fraps before to see the frame rates of aero before, by choosing the option to check the windows aero frames per second.
those frames per second show up lower than 30 for things such as right-click menus, but it doesn't affect the performance any.
for instance, i can watch a video on youtube & see 60 frames per second for a 60fps youtube video - or i can load up a video player and see the correct frames per second from that program too.

when you say the frames per second are unusable, are you experiencing things such as the windows fading in or out & they are stuttering along the way?