Ram

my desktop was running on 128mb of sdram pc133 so i bought some more ram 256mbx2 sdram pc133 legend sticks and installed them in computer but it wont boot.
my motherboard is asustek tusi-m and says can take up to 1 gig of ram.
When I put just one 256mb of ram in computer boots ok.
sometimes when two sticks installed the screen displays lots of lines and once it recognised one stick but not the other.
is this a bios problem ?
the ram appears fine but not when booting together do i need to change bios setting?
if some one could please help here.
regrds windowsdoors