Much point in upgrading my OS for more RAM?

[Jango]

I have 4GB DDR2 667MHz RAM in my system atm but obviosly it only counts for 3.2GB as I have Windows Vista Home Premium X32 Bit.

Is there much point in upgrading my OS to X64 bit? How much will it cost and where will I get it from?

Thanks in advance.

 

[Jango]

The OS came installed on the PC when I bought it in September 2007. Does this mean that it is full retail? I didn't upgrade it from earlier versions.

If I can get a x64 disk for £7, can you send me a link to it please?

It's good I only have to pay £7 for an extra 800MB of RAM.

 

[Jango]

It is a MESH PC.

Is there any other way to get x64 bit or to make my computer actually use the whole 4GB of my RAM?