I express my gratitude to ryuu123 for his/her all efforts...
Finally I succeeded in installing Snow Leopard on my Vaio P. I'm not familiar with Mac nor sure that my steps are correct, but at least it works fine (of course there are still some problems such as "About this Mac"). I hope the following is helpful for those who are still in their effort.
1. ryuu123's files (vaiop20090910)
2. Chameleon 2 RC3 with installer
3. Kext Helper b7
4. USB Memory A 8GB above
5. USB Memory B
6. OS 10.6 DVD
[Making Installation Disk]
1. Format USB Memory A (HFS+, MBR)
2. Restore OSX DVD on USB Memory A
3. Install Chameleon 2 RC3 on USB Memory A
4. Copy ryuu123's files to USB Memory A
[Preparation USB Memory B]
1. Copy ryuu123's files to USB Memory B
2. Copy Chameleon 2 RC3 with installer to USB Memory B
3. Copy Kext Helper b7 to USB Memory B
1. F11 -> Boot from USB Memory A
2. Install -> Reboot
3. F11 -> Boot from HDD/SSD with "cpus=1 -v -f"
4. Set up
5. Insert USB Memory B
6. Install Chameleon 2 RC3 on OSX
7. Open Terminal
8. Copy the following files/folders as superuser
Now you can boot without USB Memory A.
9. Install 2 kexts (GMA500BacklightDisplay.kext and VoodooHDA.kext) with Kext Helper b7
10. Open Terminal
11. Delete AppleHDA.kext as superuser
For dual boot (OSX10.5.6 and W7), I used PC_EFI V9 Chameleon 1.0.12 (UInstaller). I'm not sure it still works fine on Snow Leopard. I really love my OSX on Vaio P, and deleted Windows