Windows dual boot installation question

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http://askubuntu.com – OK, i have windows 7 installed, i don't know weather or not it is in a partition in my c drive, but i have 450gb free space. when i install Ubuntu does it use ALL of the free space as a partition for Ubuntu, or does it just use what ever amount in needs. i just want it to partition itself, like so it would know how much to give itself instead of it just taking all the space for itself. my windows installation takes up 51gb of space. (HowTos)