Removed dual booted XP, "Reboot and select proper boot..."

Hi! Alright, so I screwed up big time. I had Windows XP pre-installed (C:) when I bought the computer nearly 3-4 years ago.Then I dually installed Windows 7 to a logical partition (D:), and then experimentally installed Windows 8 Pro WMC (G:) to the last partition, which is currently the default. I needed some space, so I decided to remove Windows XP, and like an idiot, formatted the C:...