Hi, I hope someone can help, I'm trying to upgrade my memory from 2 x 512mb (1gb) to 2 x 1gb (2gb) the 512mb ram is pc2-4200-444-12, the 1gb ram is pc2-4200-cl4, they fit into the slots perfect, my motherboard can take upto 4gb. When I tried the 1gb ram it wouldn't do anything, when I try to boot it, theres no beep, but a loud buzzing. I was told these would be ok, but obviously there is something wrong.

Dave, July 2011

Dont know what happened, but its all working now lol, thanks for your help Electro

Dave, July 2011

Put back your original memory sticks. Does it work if you ONLY install a single 512 Mb stick? Do you need to use the 2 sticks?

Go to this site: http://www.crucial.com/
Go on the Memory (RAM) title and click on scan my system. You'll get a download for a small utility that will tell you exactly what your mother board and BIOS do support as RAM. Run it.
(the documentation for my motherboard claimed 2 Gb capacity, it's realy 1.5 Gb)

You tried using 1, 1Gb stick, try using 2. If you have dual channel RAM, your RAM must be installed as matching pairs.

The loud buzzing is absolutely abnormal! Normaly, the sound for faulty RAM is repeated long beeps. It may be that that stick is worst than faulty. Return it to where you bough it and get a refund or a replacement.
If you have a rather dumb BIOS made for dual channel RAM with no provision for a legacy, single channel, configuration, it may try to access an uninstalled second RAM stick... This could explain the buzzing sound.

Check the timing information for your original and new RAM. Maybe your BIOS don't support the needed timing requirement of the new RAM.

If you have 4 memory slots, you probably can keep the original RAM in addition to the new RAM, making you go from 1 to 3 Gb.

Electro, July 2011