can I edit the boot.ini in XP so not to boot in GUI mode?
No - You need to create a boot floppy and change bios.
Prior to the release of Windows XP, all Windows versions included MS-DOS. While you can work with a DOS command prompt in Windows XP, there is no way to restart this operating system in MS-DOS without a boot disk. You can create the MS-DOS boot disk on a floppy disk using the tools in Windows XP. To boot from a floppy, you must assign a higher boot priority to your floppy drive than to your hard drive in your system's BIOS setup program. Windows XP is also capable of booting in safe mode with a command prompt window only. While this is not the same as booting directly into MS-DOS, it may be helpful in some circumstances.