strange one but need to go back from exchange 2k3 ent to standard

[McBunny]

we hit the 16gb limit on a exchange server the other day so we thought great upgrade to enterprise and thats it sorted so we did and it worked

but not management have declined the spend so i now need to go back to standard version but has anyone done this (id imagine not) or know how one may go about it without having to completely remove it and start again if at all possible