Can not use 1 gig memory stick in slot?

A friend of mine has a MSI KT6V motherboard which seems to have porblems with it's memory slots (it has two). Slot one seems to work okay, but will only use up to a 512 mb stick (pc3200)in slot one. Slot two seems to have issues. When I tried a brand new (simpletech 1gb pc3200 stick) 1 gb stick the machine would to a bootup check (even memory) but when it would suppose to be going into windows, all that would show up is a blinking curser in the upper left corner on a black scrren. He has been running wndows xp with just the kingston 512 memory stick in it with no problems, but I still cann't figure out why the 1 gb stick won't work.