Windows XP very slow to load

I use XP home and it is configured for 3 users. After the login is done, it takes one minute (almost exactly) to load the remaining of XP. It does that with any of the 3 users (2 full + 1 restricted user). When one user account is open and we switch to ano
ther user without closing the 1st account, then the 1-minute delay does not exist.

I looked into all the programs that start automatically and I cannot eliminate the program or service that causes this delay. This delay was not there when I first configured the various users.

Any idea of what may cause this 1-minute delay?