Help macbook pro flashing question mar folder on startup?

-Hey guys i have a problem, i was messing around with my mac to try and install os x onto my netbook and during the process i might have tweaked with the system a little bit, now whenever i start it up it always shows a flashing question mark. I reinstalled os x and reset the pram but no luck. I also ran the disk utility repair thingy but it didn't help. I think it has to do with the start up options, like i think i might have set it to start up from a usb or something, how can i fix this?Even if you set OSX to boot from USB, it should look elsewhere (like on your hard drive) if it doesn't find a bootable system there.



Troubleshooting tips for addressing this problem are covered here:



http://support.apple.com/kb/TS2570



In brief, the steps in increasing order of pain-in-the-xxx are:



1. Disconnect all peripheral devices, if any, and try again.



2. Boot in Safe Mode by restarting with the Shift key held down. This resets some things. Then restart again and see if all is well.



3. If not, reset the PRAM by restarting with the Option, Apple, P, and R keys all held down. (I know you tried this already.)



4. If that doesn't help, boot from your OSX installation or system restore disk by inserting the disk in your DVD drive and restarting with the C key held down. Then, run Disk Utility to repair the hard drive and then repair permissions. (Here, too, I see you say you tried this, but you have to boot from your DVD drive to repair the drive.)



5. If that doesn't help, re-install OSX. You can do this without losing your apps, files, or settings by doing an "archive and install." You'll need to run Software Update afterward, though, to get back to the most recent version of OSX.