Windows 8 on your computer, I apologize for the inconvenience. We will make sure that the issue will resolved and you will be able to install Windows 8. Before getting into the issue, thank you for choosing Windows 8 and welcome to Microsoft Community!
We need some more information. Please help us by answering the questions mentioned below
1. What is the make and model of the computer?
2. Currently which version of Windows are you running on your computer?
3. Which antivirus are you using on your computer
I would suggest you to try these methods and check the issue status.
Remove the all external devices apart from the keyboard, mouse and check the issue status.
Keep the computer in a clean boot, disable the antivirus and check the issue status.
How to perform a clean boot to troubleshoot a problem in Windows Vista, Windows 7, or Windows 8.
Note: Please go through step 3 of the Kb to keep the computer in normal startup after fixing the issue.
Disable anti-virus software
Note: Antivirus software can help protect your computer against viruses and other security threats. In most cases, you should not disable your antivirus software. If you do have to temporarily disable it to install other software, you should re-enable it as soon as you're done. If you are connected to the Internet or a network during the time your antivirus software is disabled, your computer is vulnerable to attacks.
Run the System Update Readiness Tool and check the issue status.
Check your hard disk for errors.
Important: While performing chkdsk on the hard drive if any bad sectors are found on the hard drive when chkdsk tries to repair that sector if any data available on that might be lost.