I have IBM Thinkpad T40 with 2X512MB Chips. One of that is a Kingston chip. I tried to replace this with 1.0GB Chip from Kingmax and it did not work. I called iBM and they said they don't support anything other than IBM memory. I decided to put back my previously existing 512MB Chip(Kingston) and it didn't allow to boot the system. I called back IBM and they say that they don't support that either. Later, I tried to insert this 512BM chip in another Thinkpad(T41) of mine and it gave a blue screen of error.(This BIOS is not ACPI compliant in this system etc...)
I upgraded the BIOS from IBM's support site and it went very well. Even after that, it does not recognize my previously existing Memory. I don't know what else to do. Appreciate if some one can shed some idea.