Problems loading up from different user accounts

[Helen]

I have windows xp home. It has worked well up until 1
month ago and it is now very temperamental and got
progressively worse. I have four different user
accounts. Windows only loads up using one of these
accounts, but it takes a very long time. When starting
xp from the other users accounts, nine times out of ten
the computer hangs. The only way we can access the other
user accounts, is to switch user from the user account
that lets you into windows.

Can you please give me advice.