The IT7-Max2 v2.0 uses a 845 chipset which has a banking limitation of 1 double sided module and two single sided modules. So, if you install two double sided modules in slots one and two it would render the third slots useless. The best configuration for the 845 chipset is 3 512MB single sided modules which the motherboard can see and use. How do you tell if you have a sigle or double sided module? Just look at how many components (chips) are on each side. If the black chips are only on one side then it is single sided, both sides then double sided. Since single sided 1GB modules are not released yet for main stream sales you could use 1 1GB module and 2 sigle sided 512MB modules for a total of 2gigs.
Hope this helps.