Windows 8 pre-installs are usually using the UEFI configuration. When you boot the Windows 7 DVD, use the Boot Device Menu and look for the DVD drive with a UEFI annotation in front.
Other things that might come into play, a Windows 8 install with secure boot enabled, will usually kick you out to somewhere, perhaps back to the bios until you have adjusted some settings. Hard to say for sure since they all seem to handle it differently. There may be some info on an HP users site.
I am not sure about this, but the Recovery partition on the end might be referenced as a particular drive partition. By adding another partition in front, it might effect the Recovery options for your system .. but again, no particulars available.