Advantage of using indentical RAM blocks

less likelihood of issues, they'll all run at the slowest speed but that's not a big issue.

however which version of windows are you using?
http://msdn.microsoft.com/en-us/library/windows/desktop/aa366778(v=vs.85).aspx#physical_memory_limits_windows_7

home premium can only take 16GB.

Your best bet is to buy a single package of the amount of DRAM you want, ANY time you mix packages of DRAM it can be problematic (i.e. the sticks might not want to play together), with a single set you are assured all in the package were tested to work together and especially with Intel, if the sticks are 1600 or better the XMP programming is done by packaged set - not individual sticks - say you buy a set of 2x8GB 2133 sticks in the advanced timings that set will prob call for a tRFC (advanced timing) of 208 where a 4 stick set requires around 278, so micing you may be required to manually set up the timings (both base and advanced) as well as voltages (mixed sets also often require additional voltage to DRAM and/or MC (memory controller)... in short, if it was as easy to just sticks as many purport, then the DRAM makers would simply sell single sticks and mark them up and make a ton more money - since they test to ensure all in a given package work together it takes more time = higher cost, i.e. 'normally' a two stick package will cost more than 2 single sticks purchased together, and a 4 stick package will be a little high than 2 2 stick packages purchased together

what are you using it for? 32Gb is massive overkill right now, and for the forseeable future. I'm peaking at 8-9GB out of 16, running Bf3 (for fun) and Dayz (for admin duties) along with 3-4 monitoring programs. so if you can't afford 32 get 16, if you can't afford 16 get 8, you'll still be fine, unless you are running multiple virtual machines.

with regards to being able to do this 'back in the day' yes you could, yes you still can, but as ram gets faster the margin for error gets smaller, and the greater the likelihood of there being an issue. The pain of unidentified bsods is not worth it, sell your old, start with a clean slate.

For DRAM, yes, it's best to get all you want in a single package as all are teseted to work together, and you bring up a reason why where you touch on on pricing saying a 4x4GB set is more expensive than a 2x8GB - both are 16GB, but...even the the 8GB sticks have twice as much DRAM (everything tighter, and tighter tolerances due to higher capacity, it's still much easier to pair 2 sticks to work together than it is 4 sticks, thus takes longer to test and find four that play well, so the 4x4GB cost more and to match 4x8GB takes even longer (not to mention the 8GB sticks are harder to match than 4GB sticks), which is why you'll more likely see 2 8GB stick packages are cheaper than a single 4 stick package.

On the timings, what you see is the base timings (the 4 main, like 9-9-9-27), if you delve into the BIOS under DRAM you'll also find what's called secondary or advanced timings, (many of them), most are often those that set up the DRAM to be able to play together with multiple sticks at once, in the rough example I gave with just one of them, the tRFC timing, think of it this way - above I gave the example of 208 and 278 which are fairly typical tRFC values for a set of 4x8GB 2133/9 sticks - for simplicity sake lets change the 208 to a time of 20 seconds and the 278 value to a time of 27 seconds - and lets say we have a conveyor belt - for everything to run smoothly on the line and of the conveyor belt requires 4 people places 1 box each on the belt - so the boss checks out 12 employees and finds 4 that can pace the boxes on the line at the rate of 1 every 20 seconds, but the rest can only do it at the rate of 1 every 27 seconds, so the line is set to run at 27 second intervals, while in the meantime those faster guys could go faster on a smaller belt using 2 people and do things every 20 seconds ---- so they'd be doing a 2 box line (2 sticks) faster than the 4 box line (4 sticks) but the the 4boxes (larger sets would cost more as more people required - can use this both as an analogy of why 4 stick sets costs more (testing/time) as well as why 4 sticks require a higher tRFC - all the workers have to run at the same pace to work well

I get that message with 16Gb and only 5 being used. It's probably a vram issue, every time without fail on BF3.

Let us know how it goes

to be unfair to windows that alert about resources is utter rubbish for gaming, it triggers without good reason. if you run in non aero mode then it won't do it. So whilst it is a vram issue it's nothing you can actually solve.

No worries, keep us updated