Yep, is possible that it is a boot.ini file. If you want to give that a try, it won't hurt anything:
However, let's save that as a later option and clear the CMOS as a first line of defense. O.K., so no manual, no big deal. Take the battery out (make sure which way you take it out so you can put it back correctly) for about twenty minutes, put it back in the same way you took it out and fire up the computer. That will clear the CMOS and should reset everything.
THis is a possible remedy for the boot.ini if clearing CMOS did not work:
You can boot to the XP cd and when you see the "Welcome to setup" message, press the letter R.
You will then get a DOS prompt.
Then type: chkdsk /p [enter]
When that is done type: fixboot [enter]
Type: Y at the next prompt [enter]
Then type: exit [enter]
The system will now reboot into Windows.
If for some reason that didn't work, you can boot to the recovery console .
Type: "chkdsk /r" [enter]
When done type: exit [enter].
This takes a bit longer, but the system should boot back into Windows.