wow a long explanation, and ~100% correct
for a shorter answer, yes look on the C:\ drive for teh windows folder, if it still exists then likely there is an OS that can be restored.
As long as the CD allows you to access a command prompt, the you are in the green for using it to fix the computer.
The simplist answer is to run fixmbr and fixboot from the XP cd command prompt. If there is a restorable XP partition, it shoudl find it. I wouldn't recommend this if you were planning to dual boot, but since you want to remove the other OS, this method should work just fine.
Odds are you will still be left with a multi boot as all the OS are versions of XP and should be aware of each other from the CD.
Let us know how you make out with any of the suggestions, so we can help you further