cant truncate tables with a pk/ fk relationship?
To reseed, use DBCC CHECKIDENT

DBCC CHECKIDENT ('table', RESEED, 1)


Or you'd have to drop the FK, truncate, then recreate the FK.

This is by design: TRUNCATE TABLE is simple page deallocation and constraints are not checked row by row. This limitation means you can't truncate when there are FKs.. even if you disable the FK.