I have a sapphire 7870 xt and I would like to know if my asus p8H61 mle csm r2.0 can run two 7870xts in crossfire
Not without modifying the pcie x1 slot without damaging it or the board, or buying a riser cable/card. You wouldn't want to do that anyway because the second card would be throttled pretty hardcore by the x1 slot, if you want to do it just for kicks im including a link below on how to modify the slot and a link for the cable. To be honest though your better off in the long run just buying a better motherboard and selling your old one to recoup some of the cost. You should be able to find some decent deals on newegg, ebay, or craigslist.