Debugging mode in Windows XP is a special diagnostic mode that allows the user to send debugging information to another computer via serial cable. The other computer runs debugging software to analyze the information sent from the original machine.
Debugging mode is one of Windows XP's Safe Boot options. It is accessed by pressing F8 while the system boots and choosing the Debugging option. Windows is capable of booting into Debugging mode even when the operating system does not boot normally.
Debugging software is available from both Microsoft and third party companies. Microsoft's official debugging software, WinDbg, is available as a free download on Microsoft's website. WinDbg is capable of debugging the operating system, drivers and applications, and it is more powerful than Microsoft's better-known Visual Studio Debugger.
Microsoft's debugging tools require the computer to boot into Debugging mode and connect to a second computer running WinDbg. Third-party utilities exist that allow software debugging while the computer runs the operating system. The most popular of these for Windows XP, SoftICE, is commercial software; its primary advantage over Microsoft's free software is that it is capable of debugging without a second computer. Besides the convenience of not requiring a second computer, debugging is more useful for driver issues when done within the operating system.