text: You don't give enough info for me to check to see if your computer can handle that much memory; check at www.crucial.com to see if it can.  There's a chance that one of the sticks is malfunctioning; either that it is just has bad memory, or you could have damaged one with static electricity while installing them.  First, check your specific model with crucial to see if your system can handle two 128 mb modules.  If they say you can, then test each module.  You can do this with your original module.  Put the 64 mb module in the first slot (if you can't find the marking, it is generally the slot closest to your motherboard).  Then put one of the 128 mb modules behind it.  Run your computer for a while and see if you have any problems.  If not, then try with the other 128 mb module, and run for a while to see if you have any problems with that one.  This will show you which one is causing the problem.