I currently have 2 x 512MB RAM but would like to upgrade to 2 x 2GB,
Why?
How much RAM you need for good performance is *not* a
one-size-fits-all situation. It depends on what apps you run. You get
good performance if the amount of RAM you have keeps you from using
the page file, and that depends on what apps you run. Most people
running a typical range of business applications find that somewhere
around 512MB works well, others need more. Almost anyone will see poor
performance with less than 256MB. Some people, particularly those
doing things like editing large photographic images, can see a
performance boost by adding even more than 512MB--sometimes much more.
Only rarely will going above 1GB in Windows XP improve things. What
apps do you run?
running
PC Doctor which lists all the hardware on the computer says I can take upto
4GB yet running Crucial (sp) scanner it says I can only have a max of 2GB,
which amount should I accept?
I can't tell you how much RAM your motherboard will accept, but here's
the situation with regard to Windows:
All 32-bit client versions of Windows (not just Vista/XP) have a 4GB
address space. That's the theoretical upper limit beyond which you can
not go.
But you can't use the entire 4GB of address space. Even though you
have a 4GB address space, you can only use *around* 3.1GB of RAM.
That's because some of that space is used by hardware and is not
available to the operating system and applications. The amount you can
use varies, depending on what hardware you have installed, but can
range from as little as 2GB to as much as 3.5GB. It's usually around
3.1GB.
Note that the hardware is using the address *space*, not the actual
RAM itself. The rest of the RAM goes unused because there is no
address space to map it to.