Which song plays when Alucard walks in the forest in episode 1 of Hellsing original?
It's called Kannouteki Yuuwaku No Wana Ni Hamatta Hidariashi (trans.: Left Foot Trapped In A Sensual Seduction) by Yasushi Ishii, also called as Alucard's Theme.

It's the 6th song on the first OST CD titled Raid.