The computers container is not an OU, so you can't apply policies there.
If it has to apply to everything then you should apply policies at the domain level. Otherwise you shouldn't use the computers container and should move non-DCs to an OU instead (in a Server 2003 level Forest you can set the default location of computer accounts to be in an OU of your choice, which you should do).
Leave DC's in the default Domain Controllers OU, in any case, you don't want to start moving those around if you know what's good for you.