I upgraded to windows 7 64 bit - removed the risers, took each matched pair of memory sticks and divided them between dim slot 1&2 and dim slot 4&5 this put 2 gig of the original memory on each CPU. I then purchased two (2) sets of 2 X 2 and put them in the remaining slots 3&4 and 7&8 this gave me 12 Gig on the motherboard - I turfed the risers. These days you can (if you can afford it) go up to the 64 gig limit right on the motherboard with (2 x 8) x 8. Have fun. oh yes if you do load her up be prepared to install a thermal electric cooler.