Win10-Hater

Not AV, but I suggest you take a look at Malwarebytes Free 3.5.1 which I use on my Vista system (I use it instead on AV). You can automate scans via Task Scheduler. Also, I used to use Avast Free AV (it still receives definition updates on Vista and XP), but it suddenly became glitchy at a point of time. Don't know whether it's just my issue though. One more suggestion: take a look at Clamwin AV, a wonderful, open-source AV that supports Windows 95 (yes 95!) through 10.

Update: I finally set up a Windows Vista - 8.0 dualboot on my main laptop (Dell e5420) yesterday, after planning for one month. Windows Vista will continue to be my main OS with Win8 for things like Skype, Teams, etc.etc. that don't work properly on Vista now. I originally planned on dual-booting Vista and 8.1 but seeing as Sandy Bridge CPU's are not officially supported on 8.1 and because 8.0 has some teeny tiny performance improvements and some other goodies over 8.1 (e.g, no telemetry updates, no CPU blocks, being easier to tweak visually than 8.1), I chose 8.0. With the UI tweaks necessary

Same here. This is Windows 8.0 Pro x64 transformed into Windows 7 (it actually looks a little better than the original Win7) dualbooted with Vista Business SP2 x64 on my main laptop. Will be posting my Windows 8.1 desktop screenshots from my 2 other laptops that run Windows 8.1.

My best guess is you used a third party dark theme that changes some settings in chrome://flags to make everything look dark? Also, uBO does not install even thru dev mode from an unpacked extension folder on Chrome/Chromium. It says "could not load manifest".

Yes this is Vista inside Vista. Server 2008 is on another VM (not shown in these images)

No, this does not happen on Chromium 89.0.4385.0. I installed 2 themes, Just Black and B and W to test, they do not switch off after relaunch. Tried local redirection, same case. This is on a Vista Home Premium VM updated till Jan.2020. I also tried on vanilla SP2 (actually Server 2008 SP2) and issue is absent for me.

I have been wondering, you use Firefox 78 that is not officially supported on Vista, with the extended kernel and you along with Dixel seem rather adamant to update, so you use local method. I along with @Ximonite use the system file replacement method with all Vista updates installed and we don't have your issue. Don't misunderstand me. Think about it. Also, respect @xper

Even for Server 2008 ESU updates?

I have read, I just wanted to clarify that this is nonexistent on v.68

None of this is happening with me on Firefox 68.11esr or Chrome (not Chromium) 87 on Vista Business x64.

Alternative solution: upgrade to Windows 8.0 or 8.1 (I use 8.1 on my secondary laptop), and tweak the UI to make it look like Win7 or Vista.

I would give this ten upvotes!!!

50% instability and sluggishness, 25% horrendous unorganised mess of a UI, 10% telemetry, 15% bloat. Those are the things I hate about Win10.

Obviously, from the Mega folder

Downvote. Skype is necessary for me while meet-up is not, so I can't uninstall Skype only to get rid of meet-up. Calculator crashes on me while trying to switch b/w standard and scientific modes and also while doing unit conversions. In addition, O&O ShutUp broke many things when I used it. So, all in all, Windows 10 is the worst crap ever. Nothing has changed in approx. 5 years and tweaks that can be made to 8.x to make it fully usable on a desktop computer destroy Windows 10. @monkeylove Double downvote.