The Topic header essentially says it all, though feel the need to add necessary information to make my case.
It's disguised by Microsoft in this description, a 'Compatibility update for keeping Windows up-to-date in Windows 7'.
While some may have nor see any issues, I did, and thought it had to do with an aftermarket cooler installed yesterday. Web pages would freeze for a minute & then unfreeze, apps would delay in opening, shutdown was slow.
And had I not been reading a review on a motherboard on the Newegg site while exploring for a possible Full ATX replacement MB from my current ASRock 970M Pro3, there's a chance that I may had never discovered it was that Optional update that was the culprit.
After a very specific Windows update, however, it gets confused on the operating system and will try to UEFI boot to Windows 7 and fail, giving a very unhelpful "Reboot and Select Proper Boot Device" error. This can be fixed in the BIOS (Advanced --> Boot --> Secure Boot --> OS Type to "Other OS"), but it's annoying to deal with. I have no idea why Windows rolled that update out to Windows 7 systems when it was going to flat-out brick a system with an ASUS motherboard.
Source link & in the review dated 02/28/2017 (not far back) & titled 'Be careful if you run Windows 7'.
That got me to thinking, I had installed the same update around that time, maybe it didn't fully take & was reoffered yesterday, just before I installed a Cooler Master Hyper 212 EVO & then ran Prime95 for a few hours to accelerate curing the Arctic Silver 5 (aka 'AC5') thermal solution. I actually thought had done something wrong, and went back & made sure all was right, changed the data cable to the single SSD that dual boots two OS's. There is a slight fan rattle, an issue that goes hand in hand with low cost coolers, should had went with the Noctua NH-D15S, because now will have to order one of the fans that fits it for silence (I'm a perfectionist & don't like noises).
Yet still the issue of the freezing was dogging me. Then I recall seeing those very exact words upon booting a couple of times when reading the review.
Reboot and Select Proper Boot Device
I felt that the answer was found, and after uninstalling the update two times (it was still there after the first reboot, I presume because of the install twice), presto, the issue was totally gone!
Had I not been looking at replacement motherboards & reading reviews, as I always do when consider a purchase of this nature, would have not caught the issue until it was very widespread. After researching the update, it's not exactly new, may had been one of those that I had hidden in the past. What it does do, is upload a lot of data via the Telemetry deal. Note that there's a separate update for 8.1 that does the same.
Evidently that update does so much uploading/snooping that it has an impact on system resources, and while this isn't the most powerful computer in the World, it was built with my hands, and is no slouch.
Link is also the last in my sig.
My intention on posting this, is to allow members & our followers to be aware of the issue, and if sticking with Windows 7, these type of updates should be researched before installing. Hopefully it won't become an 'Important' or 'Critical' update, since it's now hidden (both), kind of strange when two KB's of the same number are on the hide list, and even stranger, two uninstalls & reboots were required to purge these.
So if anyone is having sudden performance issues with Windows 7 as of late, ensure that this update is removed prior to further diagnostics, this may save one a lot of time & troubles.
EDIT: Added link to Microsoft source of information in regards to KB2952664.
Edited by cat1092, 11 March 2017 - 09:47 PM.