I have 98 V70 also. It came with two remote entry thingies. One that work and one that didn't. At the time of purchase, I was told that the battery was dead. Turns out it was for another Volvo in the lot. Long story short. I would have cost upwards of $200 to re-program the extra remote entry key as Volvo is the only one that can do it. I was told, and it makes sense to me, that their system is designed to minimize theft and thus they are the only ones allowed to do it.

Hope that helps.