Hi after many hours trawling the forums I found the answer as to what had happened .
In the open entourage screen when I open it up there is a file called Microsoft user data (MUD) I had moved this into one of my personal folders tidying up the opening page into work related and personal data.
In doing so the database of five years emails went into a new location.
Entourage because it cannot see it database where it expects too find it creates a whole new database in the old location and it looks like you have lost all your data.
In fact the data has just move to the location you have moved it too.
So simply grab it and drag it back to the original location and hey presto. Five years worth of email history back where it should be.
One additional object lesson I also learnt is that when the back up drive starts to make a clicking noise it is on its way out and you wont be able to recover the data, so replace it and back up as soon as possible
Hope this helps.
Paul