I'm not clear on what you're asking. Are you trying to deploy a LANDesk agent to a 2003 server or a software package to a 2003 server that is currently managed by LANDek?
LANDesk requires access to the admin share when deploying the agent. A local administrator account will have access to the admin share (C$). You do not (and should not) create a share or modify access to C$. Again, the local admin account will automatically have access to this.
Your scheduler service should have the local admin account listed as one of the accounts it uses to access the admin share on the target machines. You can put in multiple accounts if you are running in a Workgroup configuration. The scheduler service should be running as one of these accounts as well. Ideally this is a domain admin account but it can be a local admin account (as long as it's local admin on all domain workstations). From the Console (on the Core server), go to Configure - Services - Scheduler.
Confim that your scheduler service is running AS the local admin account. Ideally this is a domain admin account. Again - that local admin account must be a local administrator on your Core server AND the target machines. IF that account is not a local admin on ALL target machines, you can configure additional accounts by clicking Change Login and adding them to the Additional Credentials section.
If this is a Software distribution question, then access to c$ is not needed. Once the agent is installed, all SW packages will be copied to your sdmcache folder during deployment (C:\Program Files\LANDesk\LDClient\sdmcache). The exception to this is if you are using Run From Source in your delivery method. But in most cases a copy of your SW deployment package is located in the sdmcache folder.