I created a stripped down Windows 95 live CD that had the default shell replaced by StarCraft. I could sit down at a machine, insert my CD, reboot, and the machine would boot directly into SC.
I was terrified that I removed my OS and replaced it with a shareware point and click adventure game.
It was a great learning experience though (esp. for my German: https://moorhuhn.fandom.com/de/wiki/Dunkle_Schatten)
win+R before login was pretty useful - albeit insecure!
(Write.exe is still present in Windows 10, and redirects to WordPad, which replaced Write.exe in Windows 95.)
At least a few years ago some of this trend was still alive making little PE images that could almost be used for real desktop use on sites like reboot.pro and other spin-offs, though it seems to be a lot less mainstream than the piracy heydays during the XP era.
I wonder if they’ll ever use it to replace WinPE. They’ve had the same installer since Vista, and it probably needs a redo (it still takes forever to install Windows).
For repair/maintenance, there is WinPE (and now, live USB boot)
It is interesting how the use of these underground builds are prevalent enough to be worthwhile to compromise
Don't use its defaults though; it'll remove Microsoft Account login and Store (which I wanted because I have Game Pass for the kids).
UBCD4Win was the toolkit I used. It had all my virus scanners, data recovery apps, pretty much everything I could ever need on there. Like a Linux live CD but with Windows. Shit was brilliant!
Windows still does WinPE, but I think that is limited to OEMs and other fancy Microsoft-licensed corpos.
Unfortunately that "hacker spirit" seems to end at "must have the source code"; the same can't be said of those customising Windows and such, who definitely didn't have the source but succeeded nonetheless.
[1] I remember someone being very surprised that I patched the binary of a FOSS application, instead of changing the source and compiling it --- the former took a few minutes, the latter would've taken far more time (to get all the dependencies, build system, etc.) and possibly introduced other unwanted changes.
Patching a binary is impressive, sure, but it's the polar opposite of sustainable. You don't have a good way to document your fix, it's dependent on one exact source tree and how the compiler was feeling that morning, and even minor changes from upstream can completely change the way a binary patch would need to work.
It's great for a one-off hack, but part of the appeal of open source for many people is how easy it is for your changes to become part of the "permanent record" of that piece of software.
Nowadays it seems that a Windows ISO does not come up short of 4 GB and this tradition of "repacking" them into small, optimised, crap-free operating systems (albeit of questionable legality, but inevitably used on a machine that had a real windows license!) has been lost. I lament this.