I just bought 4 1.5TB drives to replace my 4 500GB drives in my ICH7R RAID-5 array. After installing the new drives, they all appear in the Ctrl-I BIOS config disk selection menu. Each drive shows as 1397.3GB. So far so good. But when I select all four drives, the array capacity shows as 95.8GB. Any attempt to set a higher capacity results in an error ("not enough capcity to create volume"). I can find no documentation listing a maximum array size for the ICH7R chipset. Help!
I ultimately did find the table of max array sizes on Intel's website, and PeterUK is correct about the 2TB limit on an ICH7R. I bought a new motherboard with an ICH10R (aka Series 4) chipset, and I was able to create the 4.5TB array. Note that I also had to install a 64-bit version of Windows, since 32-bit versions have a 2TB per disk limit.
Hopefully Google will index this entry so others can find it.