MacBook :: Won't Start Up After Install Audio Program

I don't know the exact specs of my computer but it is the macbook just before the new ones came out from stock, so no parts are replaced/upgraded. Literally 10 minutes ago my computer was running fine and I was installing this program called JACK because one of my audio programs I run needed it. So after I installed it told me to restart so I did. then when I did it booted up into my empty windows partion, now it's a long story why I have a partion without windows installed but we can talk about that later. So naturally I was like "crap" and restarted but I forgot which button was to choose the start up disk so I held control-option-command hoping one of them would register... nothing happens. And now whenever I try to restart my computer I just get to the gray screen. I have tried every safe-startup-command-line thing out there and I don't get past the grey screen. If I hold down option/alt then I get a mouse(yay) but nothing else. If I hold down the mouse button then I get stuck at the apple symbol. So my question is if anyone has had similar problems and has fixed them. Oh ya, I also don't have my install disk with me.