[ubuntu] Gparted not making a partition

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http://ubuntuforums.org – Hi so im kinda new to Ubuntu. i have just bought a new computer a dell insprion 5721 and i have been having some troubles cause of win8. This was probaly the wort thing i have ever messed around with. so i want to install windows 7 and have ubuntu as a dual-boot. right now i have ubuntu installed and etc. but when i go and try to use gparted to make a new partition so i can install win7 it wont let me resize. i know i have enoough room to do it cause i have a 1tb hard drive. plz plz let me know how to fix this cause i need to get win7 installed for school thanks (Hardware)