  We consider a semigroup of operators in the Banach space $C_b(H)$ of
uniformly continuous and bounded functions on a separable Hilbert space $H$. In
particular, we deal with semigroups that are related to solution of stochastic
PDEs in $H$ and which are not, in general, strongly continuous. We prove an
existence and uniqueness result for a measure valued equation involving this
class of semigroups. Then we apply the result to a large class of second order
differential operators in $C_b(H)$.
