Ref: to your error message:
"Client Service for Netware has disabled the Welcome Screen and Fast User Switching. To restore these features, you must uninstall Client Service for Netware.
" Here is what Microsoft Knowledge Base says:
If you depend on accessing a Novell network and need the Client Service for Netware or the Novell Client, you cannot use the Welcome Screen or the Fast User Switching features of Windows XP."
Are connecting to a Novell network? if not then uninstall netware client. Here are the following steps:
1. If you are using the Novell Client, see the following the Novell support Web site for instructions about how to uninstall the service: http://support.novell.com
2. If you are using Classic view in Control Panel, double-click Network Connections. If you are using Category view, click Network and Internet Connections, and then click Network Connections.
3. Right-click each connection that you have, and then click Properties each time.
4. On the General tab of each Local Area connection, highlight Client Service for Netware, and then click Uninstall.
5. In the Dial-up Connection Properties dialog box, click the Networking tab, highlight Client Service for Netware, and then click Uninstall.
6. Restart the computer.
7. Open Control Panel, and then double-click User Accounts.
8. Under Pick a task..., click Change the way users log on or off.
9. Click to select the logon and logoff options that you want: Use the Welcome Screen or Use Fast User Switching
Source: Microsoft Knowledge Base Article ID:315347