|I haven't yet been able to exactly relate code 21 to your particular spec but it does seem that codes starting with 2 are memory related. There are a few things you could try:|
Clean the RAM edge connectors with a soft pencil eraser then pop the stick(s) in and out a few times to ensure the sockets are free of oxide.
If you have more than one stick of RAM try them one at a time.
Run this RAM test:
Always pop back and let us know the outcome - thanks