I actualy played Darksouls on my old pc, had 2.4ghz (singlecore) and 2gb ram, windows xp 8D
Had a real old ati card, cant remember the model anymore... was downrated to middleclass back when i bought it, around 2008-2009 maybe, i dont remember.
Now, Darksouls aint the prettiest game but it did tax my old pc quite alot xD