Yes, this happened after I tried to install Windows. There was only one partition to choose from, and I figured it was the one Boot Camp made...
I tried holding option down, I just get a blank screen.
Edit: I got the option to reinstall Mac from my disc after holding down option. Is my other OS definitely gone, though?
Edit 2: It asks me where I want to install my Mac OS, but there is nowhere to choose from. The window is blank.
You're going to have to erase the disk, format, and then reinstall OS X. You may have accidently overwrote your OS X partition and now it's gone.
Boot with your install media (Leopard DVD 1) but instead of entering the OS X installation process, escape out of it and select Utilities from main menu. Then select Disk Utilities. Check to see if there are two partitions showing or just one. If a second partition shows up, erase it and drag the line so that the entire drive is one partition.
1. Select the entire drive from the right side and then choose erase at the top of the screen.
2. Now select the format: MacOS Extended for Mac use only.
3. Name the drive MacIntosh HD
4. Click on erase at the bottom of the screen, then click erase again on the second window. Should take a few minutes before it's done.
5. Now you can proceed to install OS X and all your applications. Be sure to run update after installation is finished.
Note: If you made a Time Machine backup before all this happened, you can skip step 5 and restore instead of having to install OS X and all apps again.
Regards.