Sorry to resurrect this but my current testing with DS1 is relevant.

I installed Legends of Aranna on the following machine:

ASRock 775Dual-VSTA
Pentium 4 640 @3.2Ghz
2GB of DDR2 667
GeForce GTS 250 (PCI-E)
240GB SSD
Windows XP Pro SP3

Even running on a system like this one, Dungeon Siege still only pulls off an average frame rate even when nothing is happening of about 45fps.

Just like everyone else the resolution doesn't matter, and it even still runs the same with the HD texture pack mod. Very strange!