Accidently installed grub to usb

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http://askubuntu.com – While doing a fresh ubuntu install (dual boot with XP using resize), I somehow managed to install grub to the source usb instead of to the harddrive. Normal harddrive boot goes straight to XP. Booting from USB leads me to grub. From there i can boot into ubuntu. Pretty cool actually, but not what I had in mind. How do I install Grub to HD? How do I recover my USB? (HowTos)