It's called the OSx86 Project, and it's basically an online community working to run Mac OS X flawlessly on an Intel-based PC.
However, the fact on whether it's legal or not is still being debated (I personally think it's a sketchy proposition), you can really mess up your computer if you don't know what you're doing, and the OS is really picky over hardware.
What about these specs?
OS: Windows XP Pro SP3
CPU: Intel Core2 Duo E7400 @ 2.80GHz
RAM: 3072MB
Video Card: NVIDIA GeForce 8500 GT 512MB
Monitor: Benq T221WA (1680x1050)
Well, actually, your GPU and motherboard also need to be of compatible specification...
You're GPU actually looks good (nVidia cards are great for Mac OS X), but if you're running a proprietary system (Dell, HP, etc.) or have an incompatible motherboard, it will be a no-go.
Don't forget to back up all of your stuff though, and no, I don't say that to scare you, but it's one of those things where you may need to wipe your drive completely if you mess up.
You've heard of the saying "too good to be true". Well trust me you will end up with a lame system where you'll spend hours and hours and hours in the forums and still have a buggy system. It's a friggin nightmare.