YouTube Downloaders still working under Windows XP
Here are some recommendations for YouTube Downloaders still working under Windows XP (and presumably under Windows Vista, too):
yt-dlp for Windows XP with a CPU which is equipped with an instruction set of SSE2 or higher. Credits to @nicolaasjan.
youtube-dl for Windows XP with a CPU which is equipped with an instruction set of SSE only. Credits to @nicolaasjan.
3D Youtube Downloader (free of charge). The version I am using is now 1.22.2. Starting with this version or one before, this downloader now uses the yt-dlp provided by @nicolaasjan.
YouTube Downloader HD 3.7.0.0 (free of charge). There are two versions, an installer and a portable one. These are the last XP-compatible versions. This downloader does not use yt-dlp or youtube-dl.
Youtube-dl GUI 0.4 (free of charge). When calling up the executable youtube-dl-gui.exe the first time, a folder youtube-dlg will be created under Documents and Settings\your username\Application Data where you have to replace the file youtube-dl.exe by @nicolaasjan's XP-compatible yt-dlp file. Be aware to keep the original file name!
Allavsoft Video Downloader Converter (commercial). The version I am using is 3.25.3.8409 but there are newer ones like for example 3.26.1.8768. Inside the main folder, you have to replace both files youtube-dl.exe and yt-dlp_x86.exe by @nicolaasjan's XP-compatible ones. Be aware to keep the original file names!
ytBATCH for Windows XP - A fork of ytBatch by @AstroSkipper which is a YouTube video and audio downloader script (actually rather a batch script ensemble).
And these are by no means all the YouTube Downloaders that still work under Windows XP. So, there is no need to watch YouTube videos inside browsers under Windows XP on weak computers, although this is of course possible, too.
Cheers, AstroSkipper