Is my DualChannel running and working at top performance?

Hello,


PC SPECIFICATIONS:
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PC Model :: Dell Dimension E521 (stock MOBO)
MotherBoard ID w/ date (generated from EVEREST) ::  12/09/2006-C51MCP51-6A61HM39C-00
OS :: Win XP Home
CPU :: AMD Athlon(tm) 64 X2 Dual Core Processor 5200+
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https://www.experts-exchange.com/questions/23822954/Running-Dual-Channel-Dimm1234-or-juat-Dimm1.html

This is an extension of a topic I started a few weeks ago which was closed, but I was hoping to confirm something in relation to my current setup now.

I just basically want to confirm:

1) I am running in dual channel.

2) I am maximizing the dual channel with the memory I am using.

I've already determined my dual is activated by 2 memory chips in slots 1 & 2. But I have 4 slots.

Below depicts my current setup the lines represent my memory slots:

Slot #4> [ --------------------------------------------------------- ]   -->  1GB  Kingston PC2-5300 333Mhz
Slot #3> [ --------------------------------------------------------- ]   -->  1GB  Kingston PC2-5300 333Mhz

Slot #2> [ --------------------------------------------------------- ]   -->  256MB  Nanya PC2-4300 266Mhz
Slot #1> [ --------------------------------------------------------- ]   -->  256MB  Nanya PC2-4300 266Mhz

What I need to know if I would be better off removing 3 & 4??