I have a really old computer that uses SD ram. It has 512 mb of ram and i got more to add on. When i installed the ram, i got keyboard failure. I also tried another stick i have and it was the same problem. The only ram that works is the one previously installed.
Here are my computer
Dell OptiPlex GX240 Series Desktop/PC.
Memory Type: SDRAM, PC133, SDRAM (non-ECC)
Maximum Memory: 1GB
Currently Installed Memory: 512MB
Total Memory Slots: 2
Available Memory Slots: 1
Name brand computers of that era are notoriously picky when it comes to RAM. Odds are you can only put RAM in the system that is specifically made for it, other types of RAM will either cause odd problems or just won't work.