Windows 7 - Need help upgrading RAM

Wasnt sure where to put this at so here go's.

Looking to upgrade my RAM from 4 gig up to 8+ Gig. Not sure what I would need to know other than current RAM in the rig is PC2-6400 400mhz 2gigs. I was looking at a the user manual and found this:

System Memory support
Supports dual channel DDR2 533/667/800, and up to 1200 MHz SLIReady
Memory. Supports up to 8 GBs DDR2 memory.

However I have no clue as to how I would go about selecting proper memory amount / type that would support it, pin amount, ect ect. Could I use:
8GB (4 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400)


Or would that not be compatible.

Go to crucial.com and there you will be able to find your RAM using their plug in that scans your system. Of course you must be using the computer you want to buy RAM for.

Download the Crucial memory scanner.

It will check your current setup and advise the best options.

SDRAM, DDR2 and DDR RAM memory upgrades from Crucial.com

If you don't require 8GB, then I would skip it since DDR2 is phasing out and is more expensive than DDR3 and won't be usable in a new system if/when you decide to upgrade.

@Zepher:

If that is the case then I would have to get a whole new mobo wouldnt I? Or would my current one still run with DDR3? Not overly excited at having to dish out a couple hundred for another mobo.

DDR3 is keyed differently so it won't go in a DDR2 slot.

What I am saying is, don't buy it if you don't need it, since DDR2 won't work with newer motherboards and will be a wasted investment, unless you can find it really cheap.

Newegg.com only has 3 sets of 4x2GB and they are $90, $140, and $150, and only 2 are in stock.