i am using an Asuslaptop series A54C MEMORY 4gb hdd 500gb os win7premium.i downloaded windows8 pro but i can,t install or run thisCOL

Notes:
* Gather all important application discs and hardware driver discs you might need to be reinstalled.
* Check the manufacturer and software developers website for updates available and to find out about the status of compatibility with Windows 8. It is possible that if the software is compatible with Windows Vista it will likely work with Windows 8 since they share the same driver model.
* If you are using software such as iTunes or Adobe programs, remember to deauthorize and deactivate them before running setup.

When making significant changes to your computer such as an upgrade, it is always recommended you backup your system prior to installing a new version of Windows. Thankfully, all editions of Windows 7 includes system imaging, which means you can backup your entire Windows 7 installation and restore it if it fails. Learn more about how to backup your Window 7 installation here

In addition to System Imaging, you can backup just your personal files using Backup and Restore, to do that, check out the following article:

http://notebooks.com/2010/12/27/how-to-backup-to-an-external-hard-drive/
http://notebooks.com/2011/02/25/how-to-restore-a-backup-from-an-external-hard-drive-in-windows-7/
If you want to backup themes, wallpapers and other minor features, Windows Easy Transfer is another option, you can learn more about it here

What you can do before attempting the upgrade?
You can do some pre-requisite tasks to ensure a smooth migration from Windows 7 to Windows 8. If you are using a name branded computer such as a Dell or HP, go to the manufacturers website for the model computer you are using and download the latest available drivers for that computer. Store them on a disc or USB thumb drive. Important drivers you should try to obtain include Network and Video Drivers. Its possible that they might just have Windows Vista or Windows 7 drivers, those will work with Windows 8.

Other things you can do:
1. Uninstall any security software before attempting to upgrade.
2. Disable any encryption software you might have installed.
3. Disable/uninstall disk utility software such as DVD/CD burning utilities or third party defragment programs such as Perfect Disk.
4. Make sure your computer is updated (devices and applications).
5. Disconnect any external devices before installing.
6. Check your hard disk for any errors:
- Click Start
- Type: CMD
- Right click CMD then click Run as administrator
At the Command Prompt, type: chkdsk /r /f
Exit the command prompt.
When you restart your system, your computer will be scanned for errors and attempts will be made to correct them.
7. Another thing you can do is disable Start items:

* Click Start
* Type: MSCONFIG.
* Hit Enter on your keyboard
* On the General tab, click Selective Startup.
* Under Selective Startup, click to clear the Load Startup Items check box.
* Click the Services tab, click to select the Hide All
Microsoft Services check box, and then click Disable All.
* Click OK.
* When you are prompted, click Restart.
* After the computer starts, check whether the problem is resolved.
Run the System File Checker utility.
SFC/Scannow checks your Windows installation for errors and corrects them. This will help with ensuring that a smooth upgrade occurs.
Click Start
Type: CMD, from the results, right click CMD
Click ‘Run as Administrator’
At the Command Prompt, type: sfc/scannow
This will check for any integrity violations
Restart your system