Computer won't boot after memory upgrade

[tankleton]

I am posting in hopes of finding some help in upgrading the memory on a desktop. I was tasked with helping a friend upgrade his desktop pc and it's becoming rather difficult.

I am trying to upgrade the memory on a Compaq Presario SR1903WM. The system has 4 slots for memory, and currently has 4 sticks of 256 MB memory installed, and is working fine. I wanted to upgrade the memory by 2GB, and I purchased 2 sticks of 1 GB memory. After installing the new sticks, the computer won't start and just beeps continuously. I was told there is some sort of post code to pay attention to but I'm not sure what that means.

There are a few things I found rather strange:
The manufacturer recommends PC3200 DDR400, with a maximum of 4GB total allowed for the PC.

Inside the PC are two different types of memory, 2 sticks labelled 256MB PC3200/DDR333mhz and 2 sticks labelled 256MB PC3200/DDR400mhz. The computer recognizes all of them, but when the computer is started with only the DDR400mhz sticks installed, it won't start. If the DDR333mhz is the only sticks installed, it will start.

The sticks I bought to upgrade the computer are labelled as 1GB Samsung 128x72 PC3200R 2.5V DDR 400 MHz ECC REG 184 pin DIMM.

I thought I followed all the right steps and have upgraded many PCs before by simply buying the recommended ones online and installing them without any issue, but now I'm stuck. Any help would be greatly appreciated!

 

[cin19]

Your PC use the non-ECC memory, when you install the new one that is the ECC that will cause the PC doesn't boot.

ECC RAM use on the Server Motherboard, and non-ECC RAM most use on desktop and laptop.

 

[geofelt]

Ram is sold in kits for a reason.
Ram from the same vendor and part number can be made up of differing manufacturing components over time.
Some motherboards can be very sensitive to this.
That is why ram vendors will not support ram that is not bought in one kit.
Although, I think the problem has lessened with the newer Intel chipsets. Still,
it is safer to get what you need in one kit.

You want documented ram compatibility. If you should ever have a problem, you want supported ram.
Otherwise, you risk a finger pointing battle between the ram and motherboard support sites, claiming "not my problem".
One place to check is your motherboards web site.
Look for the ram QVL list. It lists all of the ram kits that have been tested with that particular motherboard.
Sometimes the QVL list is not updated after the motherboard is released.
For more current info, go to a ram vendor's web site and access their ram selection configurator.
Enter your motherboard or pc model info, and you will get a list of compatible ram kits.
While today's motherboards are more tolerant of different ram, it makes sense to buy ram that is known to work and is supported.