Look inside the expansion bay and feel along the horizontal front edge. If there is a screw at the right hand end on that strip and to the left of the verical edge, then, if you bought the PS2 new after, say, October 2001, then it's a v5.

In that case, I am unaware of a method for playing DVD-Rs with NEO2.5.

JACK says he's done it and I've asked him to explain how.