I have a desktop with Intel Core i3 processor, 4 GB DDR3 RAM, 500 GB HDD, Dlink wifi usb, Nvidia GEForce (supported) Graphics card. I am successfully able to install Mac OSX 10.6 will drivers working fine like Sound, Graphics, Ethernet, Wireless etc.
Problem is, when I try to dual boot this machine with Windows 7, it fails. I followed this article to install Mac OSX as a single OS tonymacx86 Blog: iBoot + MultiBeast: Install Mac OS X on any Intel-based PC
Later I found this article for dual boot:
How to Dual Boot Mac OS X and Windows 7 – A Complete Walkthrough | Windows7hacker
Problem occurs when I run OSX installer (after installation of Windows 7) and it reaches the disk-utility for making partition to install OS to. It shows all partitions that I make in Windows as "grayed out" or non-editable. and it does not let me format a partition with GUID option, hence i can not proceed to OSX install. Only option I have there is to leave the "current" parition table and select "n partition" option from drop down. This destrys windows partition. Can one help me what could be wrong here?

My 2nd problem is, I want to make my Dell Inspiron 1564 (Core i5, 3 GB ram, 500 GB Drive) dual boot with Mac OSX. Can any one guide me to a trusted article or blog that can help me choose right distro, and also guide me through the installation?

Thanks in advance,