Step 1:Before starting the Upgrade

Step 1:
Before starting the Upgrade installation, you may try the following steps and check if it helps.
Unplug the external devices connected to the system, except the keyboard and mouse.

Step 2:
You may perform a clean boot on Windows 7 system and try to perform the Upgrade installation.
A clean boot helps to verify if any third party application services or startup item is causing this issue.
You may refer the following KB article to put the computer in clean boot:
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7
Note: Make sure you put the computer back to Normal Startup once you are done with the installation.

Step 3:
You may also go to the following locations to delete the folders
a. Click on the "Start" menu, and then select "Run", which will bring up a command box.
b. Type the word "temp" into the text area, and click "OK" to confirm.
c. In C:WINDOWS emp, press the keys "Ctrl", and "A” to select all files and delete the same

Step 4:
You can also perform a Hardware Clean boot to disable the devices and check if the issue occurs.
a. Click on Start and in Start search type in "Device Manager".
b. In Device Manager, disable the items in Display Adapter, Floppy disk drive, Network Adapter, Modem and Sound, Video & Game Controllers.
c. Right click on each of the devices and select Disable.
After disabling the devices and third party programs check if you are able to install Windows 8.
Once you have upgraded to Windows 8 enable the devices. Also refer to the computer manufacturer website and install the latest version of Windows 8 drivers for all the devices.

Step 5:
Uninstall any third party security software installed on the system
Note: Make sure you have the security software setup files or a disk to install this later.

Step 5:
If the issue persists, you may also try to download and run the System Update Readiness Tool.
You may refer the article to download the same.