My HP Pavillion DV9000 Laptop wont det...

When I tried first installing windows XP on my laptop, I had the problem that I already had Windows Vista on it, but wanted to delete it and install Windows XP. Whenever I tried installing XP, it kept telling me that there was no hard drive. I searched through all the forums on this topic and finally found out that I had to change a setting in the BIOS called native SATA driver support.

My assumption is that once they changed the mainboard on your PC, the bios settings changed as well. Try searching through your BIOS, it might have a similar setting that you might need to change.