I've installed Mac OS X 10.5.8 on my machine and I'm dual booting it with Windows 7 using Chameleon RC4. Both OS are working flawlessly. But I found that my OS X system drive Macintosh HD has two com.apple.boot.plist files, One in "Macintosh HD/Library/Preferences/SystemConfiguration" folder and another in "Macintosh HD/Extra" folder.

Is it normal to have two boot.plist files ?

System Spec.
GA-G31M-ES2L(Mobo)
Intel PentiumD 820 (CPU)
2GB 667MHz DDR2 (Transcend)
Seagate Baracuda 250GB SATA
RTL 8139C PCI Ethernet Card