Numerous ways to fix the Boot.ini file. Queston one - what is the file system. If FAT32, then careful use of DOS can even create a new Boot.ini. If NTFS filesystem, then a program from
www.sysinternals.com could help so that DOS can access the NTFS disk.
Then you can boot from the XP CD-Rom to fix the file. Or you can use the same CD-Rom to repair the XP installation. Just a few of the many options that come immediately to mind.