Repair Windows 8 after install ubuntu using Install alongside windows 8

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http://askubuntu.com – I installed Ubuntu 12.04.1 on my laptop. I knew that installing using the option install alongside windows 8 will screwup windows's bootloader. But I ended up installing it in that way because I was not paying any attention. So now I have a GRUB, a working ubuntu and a broken windows 8. I dont have a windows 8 installation disk as it came preinstalled. Is there a way to repair windows bootloade? (HowTos)