boot error after installation

[stephenadams]

hey, i installed mac os x 10.4.8 the other day fine but the problem is everytime I shut down after installing it successfully and using it fine when i turn my pc back on it's saying please insert proper boot media so I have to install it all over again...I've tried installing XP and then OS X so i could dual boot but the disc utility in the os x installer wont let me format the free space after installing xp and just wipes it clean? therefore i have to start all over and install one again dont have a clue whats going on...I've tried using the startup disk tool in system prefrences and setting it to the mac os x 10.4.8 icon and clicking restart but i keep getting the error saying please insert boot media

 

system specs ::

 

AMD Athlon 64 3000+

1GB Corsair DDR 400

80GB Maxtor Diamondplus 9

Club3D NVIDIA Geforce 7600 GT

ASUS A8N SLi Premium

Pionner 111D DVD Burner

 

any help at all would be appreciated