First you need to verify and if necessary change the boot order in the BIOS settings so that your PC will boot from the DVD drive (or USB device if you created a bootable USB Flash drive). You can do this by making the DVD drive / USB device the first device listed in the boot order and the hard (or SSD) drive your second device the BIOS, exit as save the BIOS changes.
From Windows 7, insert the Windows 10 DVD. If the AutoPlay windows opens, do nothing except to close it, now reboot the computer.
Press the keyboard’s space bar several times and wait for the “Windows” Logo / splash screen to be replaced (this may take some time) by the Windows 10 Language, Time and currency and the Keyboard setup screen. Make any changes (if needed) and click the ‘Next’ button.
Click on the “Install now” option located in the center of the screen.
Read and accept the License terms and click ‘Next’.
Which type of installation do you want? Choose the “Custom: install Windows only (Advanced)” option.
1) Where do you want to install Windows? Select / highlight the partition named (Win10 Tech Preview) or the “Unallocated” space you created by shrinking the Windows 7 partition.
Click ‘Next’ to continue. 2) Windows 10 will now start a series of installation steps, followed by a restart / reboot of your PC.
You can click here to see a series of screen shots of the automated installation part of the Windows 10 Technical Preview. No user input or action is required on your part or you can click here and skip to the point in the installation process where you are required to provide input.