Comedy (Not poking fun at you, just having some fun):
It's easy, just get a Sharpie and scrawl OSX on it.
or,
Place Tiger install DVD on top of the machine.
Comedy aside.
When you need an Apple with the Mac OS, you will try to get one. I am going to steer you away from a Mac and OSX. Look, first ask yourself what you want to do and what you require from an OS and hardware. Are you a gamer? Do you not want a dedicated game system? You will not be happy with Mac.
Everything that I want to do on a PC I can do on a Mac, and I think I can do it better with OSX. OSX is vary stable, and quick frankly, I like the interface. It's speedy, and so is Windows, but the integrated Hardware and OS just make the whole thing run better.
Rather than be disappointed, tell us what you want. The Dali Lama has said that people don't have to convert to Buddhism to be enlightened, even to transcend this existence. The same is true of computing. One does not have to be a Mac user to have her/his needs met.
It looks like your decision is going to be hardware dependent. You have found a cool laptop, and its not OSX compatible.
I use both WinTel machines and Macs. When I travel, I dont use either. I use an x86 based portable computer that uses a proprietary OS, but it runs for days on AAs and is really durable. It also is under 300 bucks! Great for the jungles of Cambodia or the deserts of Mongolia (next years journey I hope). I cant afford to replace my PB, so it stays state side and at sea level. In short, think about what you want and then match it to your means.
Good luck, and post what you need from a computer system.