Do you have an XP installation disc? If so, insert the disc and boot up from it. (You will need to change your boot order in BIOS to do this.) After Windows setup runs, press R to enter the Recovery Console and press the number option for your installation of Windows. This is usually option 1. At the DOS prompt, change to your windows/system32 directory and type expand X:/i386/ntoskrnl.ex_ (where X is the drive letter for your CD drive) and press return. When the file is copied, reboot and change the boot order back to floppy as first boot device, then save the change and reboot. Let me know how you get on.
Regards,
Michel