I would use service.delete rather than execute
In CRM 4
crmService.Delete(salesPersonEntityName, salespersonID);
you pass the entity name e.g. ("account") and the guid of the sales person.
in fact this is the same for CRM 2011
the service is
IOrganizationService
service.Delete(Contract.EntityLogicalName, guid);
Ben Hosking
Check out my CRM Blog
Linked-In Profile
Follow Me on Twitter!