NOOB! Simple scene involving an 2D array of spheres

Hello all - thanks in advance for anyone reading this. Apologies if it seems trivial… after all, I’m only a NOOB!
I want to create a scene with an array of say 1000 x 1000 spheres, but when I do a simple arraymodifier on a single sphere my pc quickly grinds to a halt (please dont ask why I need this array!!!)
The number of poly’s has obviously go thro the roof
I am sure there is a much easier/efficient way to do it - linked duplicates maybe?
Or some kind of grouping?
I’ve read a few articles about it but I want to know the most memory efficient way to do this
I am on ubuntu 64 Blender 2.65 - usng cycles for my main render (if that makes any difference!)
Can someone give this poor renderer some pointers as to how to set up this kind of aray without going into ‘mesh overload’!!!

Thank you

(please dont ask why I need this array!!!)
I will be cause it’s relevant to the answer. Do you just want to render the array, is the array animated ? Are there other objects being rendered. Is the slowdown in 3d view or when rendeed.

Some options.
In Array modifier just turn off visibilty in 3d view so array only visible when rendered.
Add a 1000 x 1000 vertex grid and use Object vertex Duplication (Duplication panel in Object settings)
Use a Particle system with your object as the particle

Thank you for your suggestion…
The array needs to be rendered and will have a refractive glass texture. It is not animated. There are other objects in the scene
The slowdown is in creating the array - the modifier cannot cope with such a high number and blender just crashes

I will try your options today and get back to you
Thanks again