I have a 512 and 256 stick of sd ram 133 mhz on an older computer. It is a customers for my repair business. The system was reporting missing a windows dll file, and not loading into windows after around 3 restarts each time. After the third restart, and after selecting 'last known good configuration', it would boot into windows fine. But it then would suddenly restart on its own too. After extensive testing of the hdd, ram, replacing the power supply (died on me in mid-diagnostic), and replacing the cd-rom (ate the xp disc I was reloading xp with), everything seemed to turn out fine in terms of the scan results. What did become apparent was when I have the 512 ram stick in by itself, everything boots fine, and nothing restarts, no errors occur. This is after 25 reboots (just making sure). However as soon as I install the 256 stick (which passed diagnostic test) simultaneously with the 512 stick, it starts the problems again. So after the full explanation here, my question is, is it possible for 2 133 mhz ram sticks to somehow not work right with each other? Or is it possible for the ram diagnostic to have missed something entirely. I ran 2 tests on each stick just so you know. Both passed with flying colors.