GPO is still in effect after removed GPO

Hi all,
For some reason my GPO still in effect on work station after I removed the GPO. GPO is at AD (domain level). It worked perfectly for before, each time modified the GPO or testing I moved the OU out of GP, it took effect right away till after I fixed the replication issue between Active Directory.
Now, everything works fine except the GPO still in effect on the OU. It has been like that for months
Thanks a lot inadvance
David