Reboot and select proper boot disk???

I keep getting this message everytime I try to boot. I just recently installed a GTX 760 and a new power supply.It worked before, how would I solve this?

Check the Boot Order int he BIOS. If you have more than one drive installed, it may be choosing one that is not the Boot Volume. Or, you may have USB in the boot order before the Optical drive, that will do it as well. Proper Boot order should be Optical first, then Hard drive. Some motherboards, you can add USB device in there, some of them will try to boot to it even if there is no USB installed. Can you get into your BIOS from a cold boot? That's what worries me about these new POS (and I don't mean point of sale) windows 8 boards, they depend on 8 to get you into the BIOS which is a huge fail.

(edit) I don't see how adding a new Video card would change your Boot order though. If you can download Hiren's Boot CD from the link below, you can try to boot from it, you can use Mini- XP to check your main drive to see if the MBR has been fouled up somehow. If so, you can repair it right from there, bu installing partition wizard 7. Install it into Mini XP, its just a temp install, then you can check the MBR.

If you can boot to a Windows 8 install disk, you can pull up Command Prompt and try Bootrec and fix the MBR that way. If you can find Hiren's Boot 13, it has a Windows 7 Boot loader you can use to boot to a drive that has a failed MBR. They no longer have it in the new versions.