First Download the driver:
http://www.microsoft.com/downloads/en/details.aspx?familyid=e1a87d8f-2d58-491f-a0fa-95a3289c5fd4&displaylang=en
EXEC master.dbo.sp_addlinkedserver @server = N'FOXPRO1', @srvproduct=N'Microsoft Visual FoxPro OLE DB Data Provider', @provider=N'VFPOLEDB', @datasrc=N'C:\ycsoftware.dbc', @provstr=N'VFPOLEDB.1'