Yes it is, but DX10 is also buggy as hell for LOTRO, I have the hi-res textures package, and DX10 is not that great with the game, though it makes it look better. Since they basically just tacked on DX10, I'd give it a few more updates for DX10 to actually be enjoyable.
And viiper - just get the normal client and not the hi-res texture one, I doubt you'd be able to run ultra high anyways, also your card doesnt support DX10, if you want a more enjoyable experience, I owned an x800xtpe as well, and with the same processor etc back in the day.

