This guide recommends turning off Automatic Update and System Restore - those are OK for the technically inclined but I wouldn’t turn them off on my Mom’s computer…
“The purpose of this guide is to tweak Windows XP for optimal performance, get rid of all the useless extras that Windows XP comes with, and to decrease the startup time of Windows XP.

Test System

Pentium II 350MHz
128MB RAM
2GB Maxtor Hard Drive
8x Mitsumi CD-ROM
100MB NIC

This system is a peice [sic] of crap by today’s standards, but after I tweak the install of Window XP [sic] on this system it will run faster, use less RAM, and boot up times will be lowered….

::Before

Boot up (time to get to logon screen) = 59 Seconds
RAM used at startup = 60MB
Processes = 15
Time to load after logging in = 35 Seconds

:: After
Boot up (time to get to logon screen) = 52 Seconds
RAM used at startup = 42MB
Processes = 12
Time to load after logging in = 15 Seconds”