Windows – Reverting from Windows 8 to Windows 7 or going back to dual boot

Simply create 2 partitions and install XP onto the first and 8DP onto the second.
I think you will have to do 8 second so the bootloader recognises the older version of Windows. Then when you boot up you will be able to select which OS you boot from.

UPDATE: (Taken from this question) 1. Yes, W8 supports dual boot, BUT you have to install it on another partition from bootable media (such as DVD or USB drive).

2. Do NOT install W8 from inside your OS by mounting the ISO, it will install over your primary partition WITHOUT giving you any other option (and without explicitly telling you what's going to happen).

Get the Windows 8 Developer Preview boot menu back.

1. Start from the Windows 8 Developer Preview installation medium.

2. Optionally, choose your keyboard settings.

3. Hit SHIFT+F10 to enter the command prompt.

4. Execute bootrec /fixmbr to update the main boot record just to be sure, partitions will remain.

5. Execute bootrec /fixboot to update the boot sector of the system partition.

6. Execute bootrec /scanos to add known OSes to the boot configuration data.

Get it to list Windows XP.

6. Execute bootrec /rebuildbcd, this will rebuild the boot configuration data.

7. If that doesn't work, reboot and use bcdedit from Windows 8 Developer Preview like this:

   bcdedit /create {ntldr} /d "Windows XP"
   
   bcdedit /set {ntldr} device partition=X:
   
   bcdedit /set {ntldr} path \ntldr
   
   bcdedit /displayorder {ntldr} /addlast
   

   Please note that you need to right click the Command Prompt tile, then click on advanced in the lower right corner and then click on Run As Administrator. Replace X: by your XP partition.

   This is native unlike EasyBCD, so the chance is higher that it would work more properly...

Good luck!