Drive MAP automatically

please check Configure Drive Maps preference logging and tracing setting under the Computer Configuration\Policies\Administrative Templates\System\Group Policy in group policy

I dont think this is a group policy preferences issue as its sbs 2003 that didnt support group policy drive maps.

1) are you running a logon script? check if the users in active directory are set to run a logon script.

SBS 2003 there will be a login script called SBS_login script and it can be found it netlogon folder

so your new DC \\servername\Netlogon folder and the script in there is what is mapping the drives for you.

I normally copy the file to a different location and then delete.

I would delete the logon script and start to run group policy preferences with security groups authentication much better system.

Here is a technet article outlining how to do so https://technet.microsoft.com/en-ie/library/cc770902.aspx

I dont like to delete anything in AD, keep the script just open the users accounts in AD and remove the script from there profiles, you can even shift click all the user accounts and remove them all at one click.

I normally delete anything, just rename it or move it out, just in case if you need to refer back to it on a later stage.