I don't know how much can fit into each slot nor what type it can hold. 
 
www.crucial.com said:  Each memory slot can hold DDR3 PC3-10600,DDR3 PC3-8500,DDR3 PC3-12800 with a maximum of 4GB per slot.* 
 
Is this true? My motheboard is ASUS P6T - SE. I have an ibuypower computer. 
 
I have 6GB of DDR3 DRAM at the moment, and desire 8GB.

You running a render farm? 
 
 
Do you have 2GB x 3...? If so, just buy another 2GB of the same type that you already own.

I have a P6T (not SE) and mine's Triple Channel.

" You running a render farm?   Do you have 2GB x 3...? If so, just buy another 2GB of the same type that you already own. "

Can you not just open the case and look at what you already own and buy another of the same? That would probably be the easiest thing to do.

 "Win 7 takes up 2 gigs of ram, so I am fixing that. "

6 is fine unless your running 1000 programs at once or trying to render the universe.

" @demontium said:

 "Win 7 takes up 2 gigs of ram, so I am fixing that. "

Win7 takes anything you give it. if you installed 64 gigs, sooner or later it would use it all up. It's cache, designed to be used up.  6 gigs is enough, save your money. "  

6 is more than enough unless your doing heavy video editing or high level photoshop (or running VM's I guess, but I doubt you are).  
 
Additionally at this point in order to retain your existing level of memory bandwidth you would need to move to a 12gb configuration, you would also need to track down an identical triple channel kit to your existing set of DIMMS to ensure full compatability.

" 6 is fine unless your running 1000 programs at once or trying to render the universe. "

yah what people said above, unless your a hardcore photoshop editor or video editor you won't be using up all that ram yet.

" @demontium said:

 "Win 7 takes up 2 gigs of ram, so I am fixing that. "

Win7 takes anything you give it. if you installed 64 gigs, sooner or later it would use it all up. It's cache, designed to be used up.  6 gigs is enough, save your money. "

If he's looking to upgrade, then there's obviously something wrong. 
 
It's probably not his RAM, but something else.

RAM only upgrades on Tuesdays, so don't install any new pieces unless it's on Tuesday. If it's raining outside, don't do it (even if it's Tuesday) because that makes the RAM less active when you first plug it in and it will never be able to perform at 100%.

Crucial is usually very good at telling you the right information on your motherboards memory capabilities.

I just wanted to know how much each slot could take. LIke if it can handle a 4 gb RAM. I want more RAM because I used to be able to run all my games at max, but some new ones are struggling. A 4 gb upgrade could help.

" I just wanted to know how much each slot could take. LIke if it can handle a 4 gb RAM. I want more RAM because I used to be able to run all my games at max, but some new ones are struggling. A 4 gb upgrade could help. "

" @demontium said:

" I just wanted to know how much each slot could take. LIke if it can handle a 4 gb RAM. I want more RAM because I used to be able to run all my games at max, but some new ones are struggling. A 4 gb upgrade could help. "

What's your graphics card? "

Are you sure you have 2 3GB sticks, or is it 3 2GB sticks? The P6T is supposed to be running in triple channel. If it isn't, you're going to want to be buying a third stick of 3GB in whatever speed matches your current setup, which you should be able to tell from looking at the heatsinks on your RAM or maybe through the BIOS.
 
 Windows 7 makes use of all installed RAM, but it's also good at giving up control of it to a memory-intensive program. There's also diminishing returns on how much RAM you have based on what you're using the system for, and for the typical user, 6GB at the moment is plenty.
 
Anyway, a good idea is to look up the specs of your board on a site like Newegg (here). 
 
 Memory Standard: DDR3 2000(O.C.)*/1866(O.C.)*/1800(O.C.)*/1600(O.C.)/1 333/1066. Basically that means you'll probably have DDR 1333 or 1066 memory in there if the thing isn't pre-overclocked from iBuyPower (that's a very loose guess, so you're going to want to confirm it somewhere. If it's a pre-configured machine, you can probably find the specs for it on their website or wherever you bought it). The maximum supported memory is  24GB, so anything under that in any configuration would technically be fine, but keep in mind that running in matched pairs is the ideal solution. Like I said, if you really do only have two sticks in there, you'd be best served buying one stick of matching speed 3GB. If you already have 3, you really shouldn't touch it unless you're keen on buying another triple-channel set of 3 sticks.

What AndrewB said is very correct - make sure you KNOW if you have 3x2 GB or not.
Running it in triple channel is desired. If you have 3x2 I'd stop trying to upgrade RAM - it's clearly not your problem.

And may I ask you - what games CAN'T you run in high detail? I am starting to think your vid card might not be up to it, even though mine is worse and I aint got no trouble so far.

Sorry the RAM is three 2 GB pieces of RAM. 
 
I want to run Just Cause 2 and Crysis in full spec and I cannot currently do that.  
 
I have a NVIDOA GeForce GTX 285 and a processor Intel Core i7 CPU 920 @ 2.67 GHz 2.67 GHz. 
 
Are you able to run games like this full spec with lower hardware?