open registry "regedit"
Go to HKEY_CURRENT_USER\Software\1C\Men of War - Assault Squad there assuming you didnt format and played on that pc before the cd key should be showing what account it was bound to.
Otherwise you may have to get gamespy arcade info is here:
http://digitalmindsoft.eu/forums/sho...l=1#post235145
and try to figure out that way which account you used.