Asena,
I followed the link that Tony (Jupitar5)gave in a previous post and purchased the memory for my PSR 9000 from Crucial Technology. The memory worked great!. After all the trial and error with cheaper memory, I was thrilled to finally get something that worked like it was supposed to. So for reliable memory that you won't have to return, follow the link that Jupitar5 has posted in this topic.
TONY, belated thanks for your help,
Kind Regards,
Dennis