You have to partition with XBPartitioner 1.1 - it's the only application that supports formatting of large (>256Gb) partitions.
You can't have 3 500GB partitions - C and E are effectively fixed, so the only ones you can mess with are F and G.
You can't have a 1.5TB partition either - from memory the maximum partition size is ~1TB (there's a thread on this, but I can't find it at the moment!)
So you'll need to split the 1.5TB into F and G, with neither partition larger than 1TB. You'll also need a BIOS that supports non standard partitions - I've seen X2.5035 menioned, but have a look through the second thread that red_ring_of_box linked to, it contains a discussion about BIOS support.
QUOTE(red_ring_of_box @ Dec 9 2008, 04:13 AM)

an F drive which contains the first 100GBs of the remaining space then the G drive which has to be unlocked first to free up the rest of the space.
The "standard" F partition is 137Gb, not 100Gb, and the G partition is quite happy on locked drives. (IMG:
style_emoticons/default/smile.gif)