If you are unable to boot using system repair disk then you need to change the boot order before reinstalling Windows.
a) Restart the computer and press F2 to enter BIOS (Options may vary according to the computer manufacturer settings)
b) The boot order should be as follows.
First Priority - CD ROM drive
Second priority - Hard Drive
Important:
Modifying BIOS/complementary metal oxide semiconductor (CMOS) settings incorrectly can cause serious problems that may prevent your computer from booting properly. Microsoft cannot guarantee that any problems resulting from the configuring of BIOS/CMOS settings can be solved. Modifications of the settings are at your own risk.
I would also suggest you to check if the media is corrupt. You may try performing installation on another computer to crosscheck if the media is corrupt.
You may also perform the following methods and check if it helps to resolve the issue.
Method 1: Startup repair
I would suggest you to perform a startup repair using Windows 8 bootable DVD or USB drive and check if that helps.
a) Insert the installation DVD or USB and boot Windows 8 from it.
b) In the ‘Windows setup’ page select the ‘language to install’, ‘Time and currency format’ and the ‘keyboard or input method’ and click on ‘next’.
c) Click on ‘Repair your computer’ and select ‘Troubleshoot’.
d) Click on ‘Advanced options’ and select ‘Automatic Repair’ and select the operating system.
Method 2:
However, before performing the steps below, try performing custom installation by unplugging all external devices. If that doesn’t work, you may follow the steps below to perform flat installation. A flat installation is an alternative to an installation that uses the Windows 8 installation CD or DVD.
a. Boot from the DVD.
b. When you get to Install Now screen click on recovery options.
c. Click next when it's looking for windows installations.
d. At the Choose recovery tool window click Command Prompt.
e. Then type robocopy "Type in the DVD ROM drive letter" then colon c:\Win78/e /h.
f. You will then get a message that says
Does C:\Win8 specify a file name or a directory <F=file,D=directory>?
Press D for directory.
This will take 4 to 5 minutes depending on the speed of your DVD drive.
g. Type c: hit enter.
h. Type CD Win8 then hit enter.
i. Then type setup.exe.
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