Q: I have just installed Net Nanny. I now seem to have lost the ability to switch between users in Windows XP, without completely logging off. Is it possible to restore this?

A: From Net Nanny Knowledgebase, I learnt that Net Nanny and Fast User Switching won't work in tandem. Here is the excerpt from that article:

Net Nanny will automatically disable Fast User Switching in XP during installation. Fast User Switching must be disabled for Net Nanny to function properly and to load up on each account. You may still set up a separate user name for each family member. However, each user must log out of their account before the next user starts for Net Nanny to function properly. You do not need to shut down the computer, however, to log out of the computer.