You can check the number of processes running on an XP machine by right clicking the tasks bar and choosing "Task Manager".
An XP machine by default will have approximately 25 processes running. If you have an XP machine that has more than 30 processes running at startup, you need to take a look at what is running and cut back.
The lowest number of processes that can run at startup for an XP machine outside of safe mode is 14 if my memory serves correctly.
Typically, if you go fix an XP computer and see more than 30 processes running at startup, from my experience either they have way too much stuff installed or they are infected with some type of malware. Nearly always the latter.