Well I have got my Win7/XP 32 dual boot system now, I had Win7 already so just added XP on another partition, had a few problems but got through it in the end.
Spent all afternoon setting XP up and downloading updates etc.
Tried to run OMSI from the folder it is in but it said it was not activated, I suspected this would happen because of the registry.
Re installed OMSI to the same folder it is in giving me proper registry entries in XP but then had the dreaded activation limit reached, so an email sent to Aerosoft.
It is a pain as it is on the same computer, wish I could of just copied registry entries from win7 to xp but would not know what to look for.
Will be interesing to see if it plays better on XP on my system, Lets hope it is all worth it after doing this.