A. If you upgrade from Windows Me or Windows 9x to Windows XP in the coming days and want to network your new PC or new OS with other machines in your house, you need to remember a few key details. Unlike Windows Me and Win9x, XP has built-in networking security, so you'll have to log on to an XP box before you can use it and, if you're wise, you'll password-protect that account. But after you do so, you won't be able to access shares on your XP box from Windows Me and Win9x machines. Here's why: In a Windows workgroup based on XP, Windows 2000, or Windows NT, you must supply valid credentials (your logon/password) before you can access network resources. And you must configure these logons and associated passwords on any XP (or Win2K or NT) machine on the network. So let's say you log on as "sally" to a Win98 machine. To access an XP machine on the same network, you'll have to set up a "sally" account on the XP box that uses the same password. After you set it up your network this way, accessing shares will work the same way it did in Windows Me and Win9x.