I wish I'd known about that 'memory management' thing years earlier...I was enjoying using older PCs for the nostalgia factor, but now I have a great reason to stick with the newer models. I migrated back to my HP Pavilion Slimline S5-1020 PC after reading your post here, sixthofmay. It has a Pentium E6800 (which is similar in capabilities to the Core 2 Duo but somewhat stripped-down), 4GB of RAM (XP only sees and uses 3GB RAM, which is more than enough for me), a 320GB HDD, and a DVD+/-RW drive. HP only has drivers on their site for 64-bit Windows 7/8, but thanks to SlimDrivers I was able to get a full suite of drivers for 32-bit XP installed (the motherboard's 100%WinXP compatible). There is still a lot of software which works very well under WinXP after all these years, and the programs I personally like to run are as follows (in a revised [and finalized] list):
-CCleaner 5.32 (the last version released before Avast acquired Piriform, and as a result unaffected by the issues which have become notorious for plaguing later releases)
-Defraggler 2.21 (ditto to the above)
-Disk Cleaner 1.8.1795 (the latest [and likely last] version of this obscure yet incredibly useful program, which covers a few bases that even CCleaner misses)
-Firefox 28.0 (the last version released before Mozilla switched to Australis; it works great as my main browser, and has no issues connecting to any modern websites)
-Mypal 28.1.0 (the best modern browser I've used on XP, and great for sites which FF28 is now starting to have problems with; I keep it on hand for Twitter & some other sites)
-VLC Media Player 2.2.8 (the last in the 2.x series; the 3.x series, in my experiences, doesn't run as well, and the extra compatibility over the 1.x series & earlier is fantastic)
-Winamp 5.8 (the newest available version of this legendary/iconic media player; while it is technically a leaked beta, the Winamp team has sanctioned it as an official release and encourages people to get it over any older versions--Winamp 6 is currently in the works, but this is the last version I will be using as it keeps the famous thunderbolt logo)
-MS Office 97 (I see no reason why anyone would need to use a newer version; after 20+ years, this is still the best suite I've used for documents/presentations/spreadsheets)
-7-Zip 18.05 (the latest version; still compatible with XP, and still perfect for .7z files)
-WinRAR 5.40 (XP still supports WinRAR with its latest version, but this is the last one I will be using as it's the last version to not have RAR5 as the default for .rar compression [pre-5.x WinRAR versions cannot open or decompress files made with the RAR5 format])
I am also using the Inexperience Patcher (version 0.7.2, which I believe is the last one unless any unofficial updates/hacks have been released since then; I would be wary of them, though), which replaces many of the built-in XP components with counterparts from Windows 2000/ME/Whistler betas, and have applied a 'Sailor Mercury' theme by Alain Gravel ("is_merc") downloaded from themeworld.com. The theme is dated April 9, 1998. Despite being 20+ years old and designed for Win95 it works flawlessly under XP, the only caveat being that I had to go and disable the maximize/minimize and restore up/down sounds (the rest are fine, but those particular sounds get annoying very fast). XP seems to be the last version of Windows which interfaces properly with these older 9x-era themes and has good compatibility with 9x-era programs without having to apply any hacks or tweaks to get them to run properly; starting with Vista it gets challenging.
Sorry about such a long message--I guess I had a lot to say! Happy Thanksgiving to all!