Download a Windows 7 64 Bit installation .iso and use Rufus to make a bootable USB suitable for installation with a GPT disk.  
Hi, I recently bought a inspiron 3542 which is pre-installed with Windows 8.1, 64 bit. My most important Medical Equipment which connects on the USB port supports only Windows 7 & when I inquired about the drivers for Windows 8 from the device manufacturer, they are not supporting Windows 8. So I must have to install windows 7 on this laptop, to get that equipment running. I've also tried installing windows 7 in Virtual mode (VMware player), but the device was not working properly. Now, the problem is I cannot install Windows 7 in dual boot environment as the disk is of GPT type & if I convert the disk into MBR, all the partitions will get lost including a recovery. Now, if I make the "Bootable Backup" of my laptop from Dell Backup & Recovery on external HDD & convert the disk into MBR to install the Windows 7; Then if required  will I be able to restore my laptop back to Factory State using that backup on external HDD?  OR is there any alternate way to install a Windows 7 (64 bit) to dual boot with currently installed Windows 8.1.
Unable to Install Windows 7 on Inspiron 15 - 3542