Re: dual boot installation on HP pavilion dv7.
If you're serious about intalling Ubuntu in dual-boot mode with Win7 and retaining the use of Win7, then read through the details below ...
You need to see the disk partitions when you boot into Win7 and use the Disk Management utility. Count the partitions you see. IF there are already four of them, that is the maximum allowed. IF you FORCE the creation of another, not only will that automatically convert the Basic Volumes into Dynamic Disks (something you do NOT want to do), it will then PREVENT the installation of Linux.
If you decide to continue on with dual-boot, then use ONLY the Win7 Disk Management utility to shrink the Win7 OS partition to make room on the drive. Win7 is very finicky about its OS partition being messed with from "outside" with other tools -- like GParted. While it may be OK, it's more likely to result in filesystem corruption, which will then render Win7 unbootable.
And, after you create some free space, do NOT format it using the Win7 Disk Management utility; leave it as free space.
Then BEFORE you install Ubuntu, use the Win7 Backup feature to create and burn a Win7 Repair CD. You might need this later if the dual-boot install corrupts the Win7 boot loader.
When you then install Ubuntu, use the "Something Else" option to allow Manual Partitioning.
Ubuntu 15.04 Mate, Mint 17.1; MS Win 8.1, Win10 TP.
Will not respond to PM requests for support -- use the forums.