windows 7 - Why is 4.5GB of my 8GB of RAM not recognised?

I have recently purchased 8 GB of RAM to upgrade my system to go along with a new shiny i5!

When I run speed checks on my system online I get told I only have 3.5 GB of RAM, also in Task Manager I only see around that value of RAM yet that stupid Windows rating index tells me I have 8.0 GB.

Am I doing/reading/interpreting this incorrectly?

See below what I see: