It takes at least a few tedious seconds to log one user off and another one on. Windows XP has an option to speed that up: Fast User Switching (FUS) lets you switch without logging off. To enable it, open User Accounts in the Control Panel, click on Change the way users log on or off, and check the Use Fast User Switching box. Now, when you select Log Off, a Switch User option appears that lets you quickly change to another account without making any users close their programs. When FUS is enabled, holding down the Windows key and typing the letter L zips you to the Welcome screen.
Beware of the trade-offs of Fast User Switching, though. You should avoid running system-level utilities, such as defraggers or indexing utilities, when another user is logged on, and if you're looking for the best performance, you don't want to let idle accounts in the background tie up system resources. The feature is best for those times when you simply need to get in and out quickly. Also note that Fast User Switching does not work if your computer is a member of a network domain.
Limit Access to the Task Manager
To prevent users from killing important processes like antivirus scanning or usage monitoring, you can use the Group Policy Editor to disable the Task Manager. Log on as an administrator and launch Gpedit.msc using the Start menu's Run dialog. Navigate to User Configuration\Administrative Templates\System\Ctrl-Alt-Del Options. In the right-hand pane, double-click on Remove Task Manager and change its status to Enabled. You can still launch the Task Manager by right-clicking on C:\Windows\ System32\TaskMgr.exe, choosing Run As…, and using the Administrator password.
This works in Windows XP Pro; to accomplish something similar in Windows XP Home, which lacks the Group Policy Editor, log on to each user account and edit the Registry. In HKCU\Software\ Microsoft\Windows\CurrenTVersion\Policies\System, create a DWORD value named DisableTaskMgr, and set its data to 1. Do the same in the key HKEY_USERS\ Default\Software\Microsoft\Windows\CurrenTVersion\Policies\System.
Network Multiple PCS
If instead of multiple users using one machine you've got several PCs in one dwelling, you'll probably end up networking them, even if only to share an Internet connection. And guess what? Windows has networking set-up and troubleshooting tools. They're in the Control Panel's Network Connections applet. Select Set up a home or small office network and Windows will walk you through network configuration, helping you choose sensible settings.
If you're trying to fix an existing network, try the Network Troubleshooter in Windows Help and Support. It's surprisingly effective.
Troubleshoot Your Network
When you encounter a network problem, some of these command line tools can help you narrow down the source. From the command prompt: