I think it'll work, but you probably won't get the best from the graphics card - if your motherboard had the PCI-E2 slot, then it would take full advantage of the card, wheras the PCI-E1 should support it, but at a reduced performance.
At the end of the day, it'll run as nicely as your motherboard will allow it, so maybe a future upgrade will be a PCI-E2 supported motherboard, and it'll all work out. There's no real option though, it's not like using a PCI-E1 card will be better. I think your as well getting the card, at least it might be ready for whatever next motherboard you buy. I wouldn't see it as running the card at a reduced rate - I'd see it as running the card at the rate it can manage, which is probably fine for most cases. Half the speed does not necesserily mean half the performance - not if the card can handle what your doing without needing all that speed.

Health, Ammo, and bacon and eggs!
