|Can't be certain but registry cleaners can and do get things wrong from time to time. |
If there was a registry entry there for prep it might have been seen as invalid (unused).
It is a bit risky to just stand back and let registry cleaners remove everything they find. My approach at first is to only let them remove entries I know at a glance to be invalid. Over a long period I then tackle them a few at a time, letting the cleaner take them out as I get a handle on them.
I generally advise those who are not familiar with the registry not to use them. Registry cleaners only remove Invalid entries and don't repair the registry. Invalid entries make precious little difference to performance because they are ignored by the system anyway.
I regard the registry cleaner which is part of CCleaner to be one of the safest ones (although not the most thorough). So far I have not known it remove anything it shouldn't - although there is always a first time.
As for the validation, see the rather convoluted fix from MS at the end of this post:
It all depends whether you are happy to go through that lot.
Otherwise if you Google "xp keeps prompting for validation" there are several hits (some simpler but only 50% success).
Always pop back and let us know the outcome - thanks