What are you trying to accomplish? Even if you'd have enough RAM to import that many addresses, my gut feeling tells me it will make your wallet far too slow to do anything. Wallets aren't designed let alone optimized for these numbers.

Did you just generate hundreds of millions of addresses and now want to check if any of them holds any balance? If that's the case, I can think of an easier solution:

• Create a list of all existing addresses with a balance.
• Find duplicate addresses between that list and your own list.

I've posted the necessary (Linux) code for it a while ago, it's very fast to do as long as you have enough RAM.