A fully updated (April 2019) 32-bit WinXP Home stripped of all unnecessary services uses about 330 MB of RAM on its own. How would I know? I'm posting from it right now
Recently I spent close to two weeks using only a 17 year old laptop for the internet. It has a Turion X2 Ultra ZM-85 (essentially an Athlon 64 X2 4400+) with 4 GB of DDR2-800 and a Crucial BX500 SSD. Totally usable for browsing, though watching videos was limited to 480p because of the crappy GF 8200M G.
But yeah, using an old 1c/1t CPU for browsing is an exercise in patience. Speaking from own experience with a Celeron D 326 and a socket 754 Sempron 2500+
My fully tweaked XP SP3 system with a Celeron 900 and an NVIDIA GeForce4 MX 440-SE (that one didn't need any RAM allocation for itself) used less than 60MB of RAM (54MB IIRC). Later when I put a more powerful Radeon GPU it needed 200MB more. Unfortunately I've lost the proof for that in the form of a task manager SS. But I still do have an SS from my not-so-much tweaked Win 7 system from a few couple of years ago:
Edit: I've found the TXT with list of XP enabled services from that time. Since most of the time I was struggling with the outdated systems always needing more performance, I tweaked the hell out of everything back then.
Cryptographic Services - manu
DHCP Client - auto
Event Log - auto
Plug and Play - auto
Remote Procedure Call (RPC) - auto
System Event Notification - auto
Windows Audio - auto
Windows Installer - manu
Windows Management Instrumentation - auto
Windows Management Instrumentation Driver Extensions - manu
Oh well, while I'm at it, I'll share some other tweaking I was playing with (also saved in the text form):
"HKEY_CURRENT_USER\Control Panel\Desktop"
- MenuShowDelay 100
- WaitToKillAppTimeout 1000
- HungAppTimeout 1000
"HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer"
- NoRecentDocsHistory 1
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
NoDrives
A: 1
B: 2
C: 4
D: 8
E: 16
F: 32
G: 64
H: 128
I: 256
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
NoLowDiskSpaceChecks 1
“HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Dfrg\BootOptimizeFunction”
- enable Y
"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer"
- AlwaysUnloadDLL 1
"HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control"
- WaitToKillServiceTimeout 1000
“HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\FileSystem”
- NtfsDisable8dot3NameCreation to 1
- NtfsDisableLastAccessUpdate 1
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\
DisablePagingExecutive to 1 to disable paging and have the kernel run in RAM
Can't remember I used the last one though, maybe.
reactions are for the Thermaltake fan (& its dust accumulation) in your side panel, because I looked at the picture & my reaction was 
