cannot recover my MacOsX from the default hard disk

hi all
this afternoon i attended a puredyne workshop and the tutor gave us cds to boot linux with puredyne on it, as it doesnt work on MacOsX. After removing the cd, the MacBookPro didnt automatically go back to MacOsX from the internal HardDrive, so I went home and enetred the MacOsX Install Disc to recover it from the harddrive. However, i didnt know i had to quit the installer in the beggining so i started re-installing MacOsX on my harddisk, when a friend told me i had to quit the installer and go to Startup and choose my hard Disk to run the existing MacOsX.

I did that but the Startup box didnt give me the option to pick my Hard Disk, it only gave me the option of running it through the Install Disc and the Network Setup. So, I cannot start MacOsX from my hard disc and i think i half installed MacOsX on a different folder.

Can you please tell me what to do cos i m without computer at the moment and afraid i m gonna lose my files too!
thanx in advance