Since I now RAM chips trust basically no longer really (the old RAM was branded goods - Samsung), I have the computer, which is now equipped with 4 pieces of KTD-DM8400B / 1G blocks, several hours with MemTest86 3.4 and Memtest86 + 4.1 through tested and in between also tested with Microsoft Memory Tester and the Dell Diagnostics CD - there were no errors. Even the "bit fade test" of MemTest (+) has passed the new RAM repeatedly.
The memory performance is loud "performance check" of PassMark also as it should be and is comparable to other similar computers with 667 MHz DDR2.