^I remember that XP SP0/SP1 was dog slow on a Pentium III that previously ran Windows 98SE.
The PC had between 128 and 256 MB of RAM, which was very high for a Windows 98SE system (when 98SE was new).
Upgrading it to 768MB made quite a difference back then.
Edit: Explanation of the odd RAM configuration.
The PC had 4 memory slots, SDRAM, I think.
Factory default was 2x 128MB (dual channel), then 2x 256 MB were added. Makes 768MB total.
Likewise, in the late 2000s, upgrading a Windows XP PC (SP2) past 2GB caused a drastic performance improvement again (boot up was almost SSD like).
So all in all, I think that Windows XP has quite some demand for RAM, to "think" properly.
I've seen it struggle on many Windows 98SE PCs that had 512MB and lesss.
If someone asks me, a fully functional XP installation needs at least around ~1GB of RAM in order to not swap to disk all the time.
Of course, a lite version running in, say, a VM will be running fine with 384 MB of RAM or something.
That's without the big driver packages and various runtimes running in background.
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