2x2GB

you will need to run a 64bit OS or a version of windows server 2003 for all the memory to be recognized.

guys, as soon as i get a good answer regarding the brand's i will buy them.
please try and help me choose...
why is there a big diffrance in price when the timeing and speed are the same?

Your system is so powerful, you really won't see a difference unless you're using some benchmark utility. However, buy the higher priced RAM to satisfy your concience, so you'll never have the thought in the back of your mind that you didn't get the best.

I doubt you will see any difference between 4 and 8 GB with current games / software. Unless you use some really memory hungry applications such as databases or some high end graphics rendering then its just not worth it.

Also, to use 4GB (or really anything above 3GB) you must go with a 64bit O/S. Windows Vista 32 generally only sees between 2.4 and 3.2GB of ram depending on your graphics card and soundcard setup (the O/S can map 4GB of addresses and add-in cards and graphics cards needs some of this for their own use so it gets subtracted from the total 4GB). This means jumping to Vista 64 or XP64.

Now, the main reason for the "you wont see any difference" is that 32bit apps are limited to 2GB of address space for themselves (can be increased to 3GB for some using different windows switches). This means that if you run a single 32bit game (only game I know that uses 64bit windows is FarCry with the 64bit patch) it will only be able to use 2GB of ram for itself. However Windows will use the remaining space for disc caches etc so you may notice the system is more responcive.

Personally if you go for some PC6400 2x2GB kit then this will allow you to add a further 2x2GB kit later and give you the best of both worlds. Also, unless you overclock its not worth getting anything faster than PC6400 (800MHz) and 2GB sticks currently dont come in anything but CAS5 moduals (really would have liked some CAS4 2x2GB sticks rather than my 4x 1GB CAS4 ones)

guys i think i'll go with 2x2GB, and see how it works for me, and just than try and deside if i want to add 2 or 4GB extra,
but again, the brand really doesn't matter?!
could be such diffrance in price and for now reason?!
ihave onlythe brand problem left!

Are you talking about this one:

Patriot Dual Channel DDR2 4GB 6400 (800MHz) CL 5-5-5-12 Eased Latency Kit - PDC24G6400ELK

There are not too many choices on 2x2GB memory modules.

Another reason you will see price differences is in the latency timings, for example memory rated at 4-4-4-12 will be more expensive then something like 5-6-5-15 which is probably around what that OCZ Vista ram is running around. The lower the timings, the 'faster' the memory is, though it's not always going to be a HUGE factor - but I'm not much of a media editing guy so I'm not too sure of the impact faster latency timings would have for you. Personally, I would find the best price for timings for 4gb DDR2-800 around 5-5-5-15 or so.