Memory only working single channel

[lastrezort]

Ok, so I wanted to upgrade the in-law's PC since they were complaining about slowness.

After a quick diagnostic, realized they only had 512Mb of RAM for an AMD Athlon 64 Processor working at a 2Ghz.

Decided it was a pretty cheap and easy fix to mount it up on the max memory the motherboard allowed (2Gb).

Motherboard is an Asus K8V-MX. It has 2 x 184-pin DDR DIMM sockets and manual (as well as Asus website) says it supports 2GB unbuffered ECC, non-ECC DDR 400/333/266 DRAM memory.

So I checked out the Qualified vendors list (QVL) in the manual AND the website and bought 2 supported 1GB sticks of Kingston mem (Part number KVR400X64C3A/1G). Got it, installed them in correctly...

BIOS and Windows XP (32bit) say I'm using 1G of mem... (should be 2G)

Upgraded BIOS to latest version (American megatrend Inc V.0501). Didn't help.
MSCONFIG "Maxmem" option is disabled.
Downloaded CPU-z. Says both are running on single channel. That got me puzzled.

Tried using old 512Mb stick in there WITH a new 1G = 1G of mem... (seems the old one is running at 512Mb (Single channel, running on 2.5v) but new one working only single channel at 2.5v).

Doubt it could be a power thing (low end power supply). It should be ok, it's mounted on a 420W PSU. BIOS doesn't seem to have any option to up the voltage on the sticks from the BIOS but they're already running at 2.5V...

Now I have no idea what to do... Any suggestions? (I'll try the sticks on another PC but in the meantime, if you have suggestions, I'll take them for sure...)

Thanks

[Train]

Use a pencil erasure to clean the contacts on the ram sticks. Then insert and remove each stick 3 or 4 times as that will tend to clean the contacts. Also use a bright narrow beam light and look at the connection that has not been used. Maybe corroded.