Windows XP has an undesirable new featurecopy protectionthat prevents you from running the same copy of Windows on more than one computer. During installation, Windows Setup examines your PC; computes a Special Secret Identifier from the exact system time plus data about key internal parts (hard drive, video card, motherboard, memory, and so on); and sends this identifier, along with your 25-character product key, over the internet to Microsoft, thereby
activating Windows XP (Figure A.5 ).
If you don't have an internet connection, you must call a toll-free number; enter a 50-digit installation ID number on the phone's dial pad; get a 42-digit confirmation ID code back from Microsoft; then type that code in the Activate Windows screen (Figure A.6 ).
Later, if you install the same copy of Windows on another PC without uninstalling the first one, Microsoft will discover your duplicity during activation and lock you out of Windows. Unless you activate XP on the second PC, lockout occurs automatically in 30 days.
Tips
If you skip activation during Setup, reminders pop up occasionally on the taskbar (Figure A.7 ). Click a reminder or choose Start > All Programs > Activate Windows to start the activation process.
Bulk-purchased corporate copies of Windows XP are exempt from activation, and many new PCs come with a preactivated copy. But new retail PCs are preactivated by a method that writes to the computer's BIOS, meaning that if you flash the BIOS (see "Check system compatibility" earlier in this chapter)
after installing XP, you may have to reactivate.
If you replace four or more of your computer's 10 key internal parts in a four-month period, you'll have to reactivate XP.
Windows stores its activation code in two small files, wpa.dbl and wpa.bak, in C:\Windows\System32 (or C:\WINNT\System32 if you've upgraded from Windows 2000/NT). If you replace your system drive, copy these files to a floppy and then copy them back to the new drive to keep Windows Activation happy.
wpa.dbl and wpa.bak are
not included in the files backed up by System Restore when you set a restore pointmeaning that after you roll back your system, depending on the depth of the damage you were trying to undo, you may have to reactivate. (I suggest, again, that if these files exist on your system, you keep a backup copy, because Microsoft isn't completely straightforward about how or why they might change.)