Compatable memory?

I have Dell C610 laptop and I want to upgrade the 384mb of ram to 768mb. I bought a stick of ram which I feel should be compatible, but it doesnt work in the laptop when I install it.

This is the ebay link to what I bought:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290201990714&ssPageName=ADME:X:AAQ:US:1123

It clearly states in the C610 manual that a 512mb stick will work, however the seller is telling me that the stick is 64x8 and my laptop may only support 32x8. Is this correct or is the stick DOA like I think it is? He wants an additional $45 for a "low density" stick and upgrading the ram isn't that important to me.

 

In many systems that utilize pc100 and pc133, the density of the memory stick is very important.

I have done numerous upgrades for clients with older machines... for instance, many older systems that the client will want to add a 256mb chip to will require a low density chip to function. Each slot on the motherboard has 2 memory banks, each bank has a finite limit. On many of these machines it is 128mb... so if you get a 256 that has all of the chips on one side of the stick it won't work, you have to get a stick that has 128mb per side.

Crucial.com lists the following as compatible RAM for a 512mb

# Module Size: 512MB
# Package: 144-pin SODIMM
# Feature: SDRAM, PC133
# Specs: SDRAM, PC133 • CL=3 • Non-parity • 133MHz • 3.3V • 64Meg x 64