I am currently having difficulty with this.  From what I know :

If you installed Windows in non-UEFI (Legacy) mode then you will only be able to boot to it in Legacy mode.  If you try to boot to it in UEFI mode it will skip the installation and only try ones that were installed via UEFI.  If you use legacy boot you should be able to get into your Windows7.

I have also read that the Windows7 installation media is bugged with UEFI mode and will not work.  I am trying to get around this atm, and have heard that using a USB rather than a DVD might work.

You will need to clean install Windows 7 and then Windows 8.

See my wiki A Clean Install of Windows 7.

Also see here:

http://blogs.technet.com/b/askcore/archive/2011/05/31/installing-windows-7-on-uefi-based-computer.aspx

Today's computers boot order cannot be changed in the bios. You must use either F12 (on windows 7 computers) or PC Settings on the Windows 8 computer. Select Advanced Startup on the PC Settings page. Reboot and you will see the Boot Menu to boot to a dvd.

Would you please report back with whether you were able to do this? I have an XPS 8500 with Windows 8 but would also like to dual boot windows 7 because my work VPN does not support Windows 8 yet. I have a separate Windows 7 license for this purpose.

Do you have any update on how you might have accomplished this? I am trying to do the same thing on a Win8 machine. I want to install Win7 on a separate partition of my XPS 8500 because my work VPN does not support Win8.  

Inside Windows 8 I hit the windows key and searched for advanced start-up option.  I selected it and then when the blue GUI boot screen came up I choose to boot from DVD drive.  After that I just followed the installation process.

I find this whole process to be quite confusing. I have many questions, hopefully you or someone can explain.

* If I were to do a clean install of Windows 7 on the system, wouldn't I lose the 3 Dell backup/restore partitions that Dell has put there for recovery?

* Why is it necessary to do a clean install of Win 7 then re-install Win 8? I am wondering if it is possible to shrink the current installation partition of Windows 8, create a new separate partition to install Windows 7 onto. Then, do a repair/restore on the Windows 8 installation in order to fix/repair the boot menu that Win 7 will apparently alter.

This really seems to be something that used to be so easy to do, but the new Windows 8 secure boot, no OS install discs from Dell, Windows 8 product key now a part of the BIOS, etc. is basically making home computing WAY too difficult. 

This really seems to be something that used to be so easy to do, but the new Windows 8 secure boot, no OS install discs from Dell, Windows 8 product key now a part of the BIOS, etc. is basically making home computing WAY too difficult.

I know and I am working with Dell to make requesting recovery media easier.

If I were to do a clean install of Windows 7 on the system, wouldn't I lose the 3 Dell backup/restore partitions that Dell has put there for recovery?

Installing another OS or changing the partitions in anyway prevents the Dell factory restore from working, so in a way if you are going to dual boot these partitions all become useless.

Why is it necessary to do a clean install of Win 7 then re-install Win 8? I am wondering if it is possible to shrink the current installation partition of Windows 8, create a new separate partition to install Windows 7 onto. Then, do a repair/restore on the Windows 8 installation in order to fix/repair the boot menu that Win 7 will apparently alter.

Give it a try if you want. In my experience dual boots usually work better older system installed first. I haven't tried installing 8 than 7 but I have done 7 then 8. The reason is that the Windows 8 boot menu might not know the Windows 7 OS is present if it is installed after Windows 8.

If it was present before Windows 8 was installed then the Windows 8 boot menu will know an earlier version of Windows is present and should display the following when you power up.

Thank you so much for your reply. I didn't realize that the Dell recovery partitions would become useless if I install Win7 on a new partition. Would it make more sense to install Win7 on a second/separate disk? That way I could keep the Dell factory image and partitions? Would I still need to do a complete re-sinall of Windows 8 after installing Windows 7 on the separate HDD?

I have a request in to have Dell ship me the media. They sent me an email stating that a supervisor would have to contact me sometime this week. I hate to be impatient, but I want to get my new computer working with my work VPN now, ASAP. I don't see why they just can't send the CD's or call me when they read my email rather than make me wait.

Also, I saw your thread on the recovery CD requests. They haven't said yet if I am going to have to pay for my CD's yet. I see you said in your post that they cost $60 to some people? I really don't want to do this, but if they try and charge me for CD's, this PC will be boxed up and promptly returned to Costco... thankfully I have the Costco customer service policies on my side.