Windows 7 uses a "new" proprietary approach on managing hard disks, Dynamic Disk (DD).
This new system is a simulation of RAID (so not new at all) plus some other gadgets most normal users will never understand the use of.
One of the differences involved is the use of a different partition description block scheme from the standard MBR, the so called Microsoft GPT.
In other words, the disk's index introduced by Microsoft differs substancially from that used by the MBR standard. Consequence of this is no other than Microsoft's tools can recognise and correctly understand where the partitions are located and what kind of they are.
Since Linux disk partitioning tools work on the standard MBR system (as most if not all other operating systems), they cannot interpret Microsoft's DD and its GPT' s index.
Consequence of this is that a DD partitioned disk is recognised as free as there is no MBR descriptor data.
Only to give a chance to recover documents and other files from DD partitions, some additions have been made to the Linux kernel already, to enable it to deal with such hard disk zones.
AFAIK further compatibility code is in the way.
Therefore don't forget that Linux doesn't need to continuously try to become compatible with Microsoft's nonstandards...
For the moment, to have Linux dualbooting, you have to force Windows to use the MBR standard and not the Microsoft's own DD.
The Linux partitioning tools can then recognize the present Windows MBR partitions and are then able to correctly install Linux and the boot code (GRUB...) for dualbooting.
Therefore this strategy is mostly valid if Windows 7 has been already installed this way.
Beware of a suspicious possible risky situation!
If you have multiple hard disks on your system partitioned with Windows 7 DD in one of the GPT modes, while installing Linux on one HD different from the first one (C: on Windows), you may be successful on having dualbooting.
The problem is that Windows 7, depending on how you have configured your hard disks, may detect a volume failure if such a volume is spanned over the physical HD now used by Linux.
You may loose much Windows data this way.
Fact is the entire volume, so not only the part physically contained by the said hard disk may be lost with all its data.
So the only rule to follow, for now, is a precise planning from Windows 7 of the MBR partition configuration, avoiding this way the use of multi-hard-disk spanned volumes, reserving the space for the Linux installation and then proceeding with the Linux install.
The big problem is the Windows user must become comfortable (!) with the Dynamic Disc system before being able to modify the partitions setup and make the necessary disk space for the Linux installation.
To conclude, the introduction of the Dynamic-Disk system by Microsoft, is not really a techniocal problem for the Linux-Windows coexistance. At the moment the Linux community is working on this Microsoft novelty to save Windows users from screwing-up their Windows systems while trying to install Linux.
To have this additional strategy fully working requires Linux partitioning tools to be aware of non standard partitioning schemes.
This maybe introduced very soon as it is a simple modification even if different Windows partition structures may require different approaches to reach a correct setup for the new operating system coexistent installation.