Mathwiz

That was a really good suggestion! So I tried disabling WebRTC by toggling media.peerconnection.enabled in Serpent to false. Unfortunately, Web.Skype.com still signed me in just fine, so I guess that wasn't it after all. I'm afraid I'm stumped on this one.

Well, I added one more SSUAO (for live.com) and Web.Skype.com works just fine with Serpent (with no add-on) but not with NM 28. I wonder if there's some obscure pref that needs to be toggled for NM 28 to work?

We just have to identify all the other places Skype connects to. It can't be that many.... Incidentally, why doesn't the add-on load in NM 28? It identifies as FF 60.9 in Firefox compatibility mode....

RAUE is an initialism for Reset Antivirus Update Engine.

A Firefox reset wipes out everything you did! Mozilla is way too happy to "suggest" a Firefox reset if you're having problems. But it resets everything; wiping out all your prefs and all your add-ons! Never do a Firefox reset except as a last resort if Firefox is completely broken and you need to start from scratch!

My apologies; apparently it takes (at least) two SSUAOs: When you browse web.skype.com, the add-on changes your user agent, but keeps it changed for every site connected to thereafter, so there may be more I haven't discovered yet.

Took a look inside; AIUI, the add-on is basically nothing more than a SSUAO: (Edit: My apologies. Apparently it takes at least two SSUAOs! Sneaky devils) general.useragent.override.skype.com = Mozilla/5.0 (X11; Fedora; Fedora; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36 general.useragent.override.skypeassets.com = Mozilla/5.0 (X11; Fedora; Fedora; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36 Try those on MyPal.

Yes, it breaks all Office 2010 apps on XP; not just Excel and Word. Even breaks free 2010 apps like the PowerPoint Viewer. I don't think it breaks any earlier versions of Office though. Well, the update you linked to is 4494528! The support page explains that it fixes a problem with an earlier update, 4486464. But AFAIK you still need to run regsvr32 MSI.DLL after installing it; I haven't heard that M$ re-released it with that mistake fixed. (Even if they did, it won't hurt to run that command anyway.)

It may not have worked because of having to use the web proxy. If an add-on filters according to where the content is coming from, everything "looks" like it comes from the proxy, so nothing gets filtered. uB0 seemed to work; it's filtering works differently.

Beware any time you see that - it's a deceptive advertisement! If you "update" you will get a PUP I recommend you install an ad-blocker add-on, so you won't see those deceptive ads any more. If you have no favorite, try the one I use: uBlock Origin: https://addons.mozilla.org/en-US/firefox/addon/ublock-origin/

To be fair, that was in 2009. I haven't seen a recent ranking; it may have improved since then.

The preference name is just general.useragent.override, not "general.useragent.overridepreference." I don't know where you got that. You are correct that it is a string. The format of a Firefox user agent string is Mozilla/5.0 (Windows NT %OSVersion%; [WOW64;] rv:%BrowserVersion%) Gecko/20100101 Firefox/%BrowserVersion%. Note that everything has to be exact, including the spacing. That's tripped me up before. Type everything in bold exactly as above. Replace %OSVersion% with: 5.1 to report XP 6.0 to report Vista 6.1 to report Windows 7 6.2 to report Windows 8 6.3 to report Windows 8.1 10.0 to report Windows 10 You can include the WOW64; to report a 64-bit Windows version (usually not necessary). Replace %BrowserVersion% with the version of Firefox you want to report. Note that versions 57.0 and above will break Instagram, as reported in that thread. However, anything below 60.0 will cause WhatIsMyBrowser.com to report an "obsolete" browser. The only way to fix both issues is with "site-specific " user agent overrides, so that you can send different user agent strings to Instagram.com and WhatIsMyBrowser.com. Please read @VistaLover's post above for the instructions on enabling those.

Which one? @roytam1 maintains several web browsers: New Moon (2 versions), Serpent (2 versions), FF 45, & Navigator.

If you did a Firefox reset, you'll probably have to recreate your userContent.css file again (or copy it from the other PC). As I understand it, a Firefox reset wipes out all customizations in your profile.

I think a batch file like this will get me by for a few days: @echo off net stop MsMpSvc echo Please ignore "At Risk" pop-up from Microsoft Security Essentials while the latest definitions are being installed cd %TEMP% if not exist mpam-fe.exe "%ProgramFiles%\HTTPSProxy\wget.exe" -O mpam-fe.exe http://go.microsoft.com/fwlink/^?LinkID=121721^&clcid=0x409^&arch=x86^&eng=0.0.0.0^&avdelta=0.0.0.0^&asdelta=0.0.0.0^&prod=EDB4FA23-53B8-4AFA-8C5D-99752CCA7094 cd "C:\Documents and Settings\All Users\Application Data\Microsoft\Microsoft Antimalware\Definition Updates\Updates" "%ProgramFiles%\7-zip\7z.exe" x -y "%TEMP%\mpam-fe.exe" *.vdm del "%TEMP%\mpam-fe.exe" net start MsMpSvc 7-Zip and wget required. Note: this is specific to my system; you'll probably need to adjust some path names, depending on where 7-Zip and wget live on your own systems.

I used to use ClamWin. It wasn't bad; my only complaint was, it's only an on-demand scanner (like MalwareBytes' Anti-Malware Free). So you have to schedule a scan every day, and there's still a chance malware could get into your system and do a lot of damage before the scan caught it. I think MSE is one of only a few free real-time AV products left for XP. That's why we're jumping through hoops trying to keep it alive. There have been occasional outages before, and IIRC it takes 3 days before the systray icon turns yellow. So you could update every other day and never see the yellow icon.

It should be "true." However, with FF 52, it won't do anything unless you add some custom Javascript:

It keeps the old definitions in a "backup" folder, I guess in case the update turns out to be corrupt. I kinda figured the new engine wouldn't work. But I guess it's smart enough to restore the backups when it blows up. (Of course, it'd be just like M$ to read this thread and decide to change the format of the definitions files, along with yet another incompatible mpengine.dll which would be required to read them. They seem to be doing everything in their power to kill off XP.)

Excellent! That's a better procedure too, because it also updates the "Definitions Last Updated" date.

I believe there are add-ons that will let you customize your UA according to the Web site. (I know they exist for Firefox.) You could then send 51.0.2704.63 to YouTube without affecting anyone else.

It looks like the mpengine.dll version has been updated too; I just haven't worked up the courage to try copying it over yet.

How is your UA modified? If you're spoofing a newer Chrome version, Google probably started using CSS or Javascript that works on the newer version, but not on the version you actually have.

It doesn't seem to be necessary to stop MSE; just stopping the service was enough for me.

I got the same message if the M$ Antimalware service wasn't stopped.