Sherry,
If I am reading your post correctly, you have created a GPO and linked it at
the domain level. You now need to not have it linked to the domain level
and have it instead linked to the OU level. If this is the case then I
would suggest that you simply unlink it from the domain level ( do not
remove and delete the GPO, just simply remove the link!!! ) and then go to
the OU to which you would like to have this GPO linked, click on Add ( and
not the New... button ) and select that GPO. You are done!
HTH,
Cary