First of all, thanks for bringing your question to the forums!
damurrelet wrote:
Question 1 - If I only replace one of the 1GB sticks with a 2 gb one - will I then be able to operate on 3 gb of ram? Or will the new one in any way neutralize the old one?
Yes it will work, but it will work much quicker if the two sticks are the same size and speed.
damurrelet wrote:Question 2 - can I replace my 667 mhz ram with 800 mhz... and if I do that, do I have to replace both sticks?
Usually you can, but the 800mhz stick will slow down to match the 667mhz RAM. Sometimes the motherboard has a maximum RAM speed as well, and this is very common with laptops. So if the motherboard has a maximum RAM speed of 667mhz, getting 800mhz either won't work, or will run at 667mhz no matter what you do.
damurrelet wrote:Question 3 - is there much difference in speed between 667 mhz and 800 mhz ram?
Not really. You might get a couple of percent performance difference, which isn't really noticable to a human anyways.
damurrelet wrote:Question 4 - I have heard my laptop (with Vista 32 bit) will only be able to utilize 3.3 gb of ram - what is with that... and is it still worth getting 4 gb then?
This has to do with how Windows accesses memory. In the 32bit versions of Windows, the numbers it uses as addresses for memory don't go up to 4GB worth of memory. It's like building more houses on a street when all address numbers for that street are already taken(sort of). You could upgrade to 64bit Windows if you like, but if you don't then any RAM you install above and beyond the approximate 3.3GB limit that Windows uses will sit there completely unused.
As for why pairs of RAM sticks of the same size and speed perform better, it's because of the Dual-channel architecture of modern motherboards. It's a technology that was developed years ago to try to reduce the bottleneck caused by memory being much slower than the CPU. It tends to work better when using identical RAM chips, but at the least they should be the same speed, timing, and size.
