Is the mac side of my computer gone forever?

i had windows xp and mac os 10.5 installed but not through boot camp. i decided to delete the windows partition with the disk utility and try reinstalling windows through bootcamp. i restarted my computer to see if the partition had disappeared but apparently both of them are non existent now. i reinstalled windows because it’s the only disk i have and when i press the alt key all i get is the windows partition and nothing else. i have already tried to reset the pram with no luck. is there any way to get my mac stuff back without having to do anything drastic?