Adding a user.

Not sure if this is the correct forum but I'll give it a try.  I'm the sole user of my Dimension 4500S.  Recently I tried to add my wife as a user to my system.   The result was my computer came to a virtual stand still.  I had to go into system restore to delete my wife, so to speak, to get it working properly.  My OS is Windows XP Home Edition.  My question is, do I need a more powerful computer, a separate computer for the two of us or what?