You can't... At least not the key combo thing. However, you can set it up so that after X number of seconds, it will default to Windows. That's really the best you can do. If you had a Mac, then we could talk, but doing this on a PC is not going to happen.
But I would suggest reading the documentation on the Ubuntu disc or online. It should explain in great detail the general process, and saves us from duplicating that effort.
I would like to dual boot my new custom built windows 7 desktop with ubuntu, but I would like it to automatically boot in windows 7 unless a certain key combination is pressed at start up, since I will use windows 7 a lot more. I would like to put ubuntu on a partition of my 500gb internal NTFS hard drive and have it dual booting, but I don't know how I would do this. Can someone please explain how to partition an NTFS hard drive, and how to dual boot it with windows 7 but boot into windows 7 without any delay unless a certain key(s) are pressed. (and I'm assuming I can install ubuntu onto my secondary partition without having to reinstall windows 7 or anything, I have the official ubuntu 9.10 installation disk).

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