Ok, after spending the last couple of hours reading the posts from searches
on "ram" and "memory", I don't know which I'm afraid of more, changing my
memory configuration, or asking the following! :-))

I mean it's been asked to death and I'm still at somewhat of a loss. So I
apologize in advance for being a bit thick!

I'm running Vista 32 bit Ultimate on a Dell E510 D820
2GB DDR2 SD Ram, (4x512MB)
BFG NVidea 7600GT-OC 256MB Video card

I've been thinking about adding memory because a couple of apps have
reported out of memory problems. One of those is a photo editing package.

Looking at Crucial today, matched sets of 2x1GB sticks are selling at
$79.95!

Question: I understand that if I install 4GB memory I will not see all of
it. But I still don't understand whether it's being used or not. Is it that
the OS has reserved the memory adresses above a certain amount and that much,
(higher), memory is just laying there, or is it that the OS is reserving that
memory for it's actual use, leaving the rest for application use? If the
latter, that seems to me a good thing.

Question: Do I buy 1 set of 2x1GB sticks and replace 2x512MB sticks for a
total of 3GB, (it seems some have had a lot of trouble with 3GB), or do I buy
2 sets of 2x1GB sticks and replace all four 512MB sticks?

Since Vista is performing magnificently otherwise, I'm kind of afraid to
mess with it period, but at $40.00 per GB...........it's just awful hard to
pass up!

Thanks in advance for your help!!

Larry