[kubuntu] Boot into Kubuntu not working

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http://ubuntuforums.org – I've a rather strange problem. I have successfully installed Kubuntu in a computer which has Windows as well. I have done this several time before and GRUB always set (k)ubuntu before Windows but for some reason not this time. So i have one disk and 5 partitions, sda, sda1(C, Windows), sda2 (D, Windows), sda5(/, Kubuntu), sda6(/home, kubuntu), sda7 (Swap, kubuntu). I've installed Kubuntu 3 times already specifying as a a booting partition sda first, than sda1 and then sda5, but all times after restart i get into (annoyingly) Windows. I checked the setting of the BIOS, but there is only the har (Hardware)