Help, about installing retail OS X Leopard on 1 (ONE) HDD

[BLA40R]

Hi, I am new in this, but I know perfectly how to install Leopard on my PC. BUT, I have a (little) trouble, I can't format my Hard Disk Drive because I have important files, and I don't want to make a Backup of my computer.

Please, I really want to know if there any way to install OS X on a single HDD. Also I don't want to buy a second one.

I really appreciate any answer to this Topic.

 

Thanks!

 

 

Oops!, I forgot, my system specs are:

 

Intel Core 2 Quad Q6600

4 GB RAM 800Mhz Corsair

NVIDIA Geforce 9800GT

Western-Digital 1x 500GB

Motherboard Intel DG35EC Media Series

 

Please I really want to install the best OS in the world in my PC.