To amend my last message here, I have a completely different setup again. This time, it absolutely HAS been finalized and will NOT be changed. It took a lot of trial and error, but now I have a collection of software that's about as good as any you will find on a given Windows XP installation. To briefly elaborate, I'm now using:
-Centaury 52.9.0 (the first [and, to date, only] public release of feodor2's Basilisk UXP fork for Windows XP; it has some bugs but is overall quite a bit better than Firefox 52)
-Mypal 28.0.1 (the first public release of feodor2's Pale Moon 28 fork for Windows XP; in my experiences 28.1.0 and 28.2.1 have some bugs, while 28.0.1 runs more stable)
-CCleaner 5.32 (the last version released before the Avast takeover)
-Defraggler 1.21 (2.21 was the last version released before Avast acquired Piriform, but 1.21 runs much faster and doesn't have the bloat/unnecessary features of 2.xx)
-Disk Cleaner 1.8.1795 (the latest version [and likely last since it hasn't been officially updated since 2010];it does cover a few bases that even this modern CCleaner misses)
-VLC Media Player 1.1.11 (the last reliable version in my experiences--slim, trim, and will run well even on my old Pentium 4 [which can't be said for the 2.x or 3.x series])
-Winamp 5.8 (the latest version--though it is technically a leaked beta, it has been sanctioned as an official release and from what I understand will end up being the last version of Winamp to retain the classic 'thunderbolt' logo as well as the classic theme; it runs just as fast as Winamp 2.79 did, which is stunning given how much newer it is)
-MS Office 97 (I could 'upgrade' to 2010 [or 2003 if I want to retain the sane interface], but 97 is doing everything I need it to do for documents/presentations/spreadsheets; its compatibility with legacy OSes [it'll work even on 95/NT 3.51] is icing on the cake)
-7Zip 18.05 (the latest version; still compatible with XP, and still perfect for .7z files)
-WinRAR 5.40 (the last version released before RAR5 became the default for .rar compression; because RAR5 is incompatible with older versions of WinRAR [and WinRAR 5.x will not run on older versions of Windows], I plan to stay far away from it)
I also have the Inexperience Patcher (version 0.7.2, which is the latest release [and likely last, since it hasn't been updated in ten years]) installed, which replaces many of XP's built-in components with their counterparts from Windows 2000 (along with some odds and ends from Windows ME and betas of Whistler). I'm also using a Windows 98 theme from themeworld.com which has the 256-color icons from 98/98SE (ironically enough, it was designed for 95, perhaps with those who couldn't afford [or didn't want] to upgrade in mind), but have applied some tweaks (restoring the default classic look and setting a different wallpaper as well as shutdown sound). All of this is running on an HP ProDesk 600 G1 SFF with a 3.5GHz Core i5-4690 (Haswell) processor, 8GB of RAM (only 3.4GB is usable in XP without tweaks, but that's more than enough for me), a DVD drive (not a burner, but since I rarely burn discs anyway that's not a big deal), and a 500GB HDD. I still have the HP Pavilion Slimline S5-1020 and DC5000 SFF PCs, and will be holding onto them since they're still fast and can definitely come in handy as spares in the future.
Mypal/Pale Moon 28 is an interesting beast as far as its programming is concerned; it's built upon the UXP engine which Centaury/Basilisk also uses (which is based on Firefox 52), but still retains some legacy code which gives it compatibility with quite a few pre-Australis extensions that haven't been properly forked to Pale Moon (like QuickJava 2.0.4.1) and ones that have (like Michael Walden's "Foxscape" theme, available for Mypal/Pale Moon as "Moonscape").
Firefox 30 is not too bad, but of course later versions are much better. If you want to watch videos in FF, I'd upgrade to a newer version (either the 45ESR or 52ESR series). I honestly don't use uBlock Origin, or any other ad-blockers, anymore...ever since I discovered Dan Pollock's custom HOSTS file, I've been sticking with and using it each day with no problems. It does what it's meant to do (keep your PC from connecting to malicious servers/networks/websites), and creates less of a sense of a guilt in that no honest/decent sites are being deprived of advertising revenue.
Sorry about the long message--I guess I had a lot to say today!