I got this from WIN XPNews, who got it from TechRepublic.com. Might be handy for installers, or on roolout systems for trouble shooting. Boot Xp in safe mode, same screen as a dual boot machine.
#1 Open the System Properties dialog box. You can do this from Control Panel (click System) or by pressing the Windows key + the Break key.
#2 Click the Advanced tab.
#3 Click the Settings button under Startup and Recovery.
#4 Click the Edit button under System Startup. This opens the boot.ini file in Notepad.
#5 One line should end with "/fastdetect" (NOT "/fastdetect /sos"). Copy that line.
#6 Paste the line you just copied below the original line. Change "WINDOWS=Microsoft XP Professional" to "WINDOWS="Safe Mode" and add the following text to the end of the line: /safeboot:minimal /sos /bootlog
#7 Save the file and click OK to exit the dialog boxes. Note: If you named the Windows XP installation folder something other than WINDOWS when you installed XP, that name will appear instead of WINDOWS in step 6.