If you have no antivirus programs installed or your current antivirus program has expired and asks money for updating, I recommend avast! Free Antivirus 2014 (aka version 9; previously named avast! 4 Home Edition or avast! 5, 6, 7 or 8 Free Antivirus), because it is free for home users and it provides good overall protection from viruses and malware by scanning also network and instant messenger traffic unlike many other free antivirus programs. Its only downside is that it requires re-registration once a year, but it is still free and not difficult.
avast! Free Antivirus works in Windows XP, Vista, 7 and 8/8.1.
If you have some other antivirus program installed, remove it first!
As more than one antivirus program makes your computer slow, it is very important to first uninstall the currently present one. Also, several well-known antivirus programs and tools by McAfee and Symantec/Norton do cause errors (for example, "Setup GUI was not initialized successfully") while installing avast! Free Antivirus. Please remove other virus protection programs completely, including scanning tools such as McAfee Security Scan.
If different errors occur, see other troubleshooting options for avast! Free Antivirus setup.
If you do not have an antivirus program installed, move down here.
If you have previous version of avast! Antivirus (such as version 5, 6, 7 or 8) installed, don't worry - your program will be updated and your license will remain intact. Move to the upgrading part for quicker installation.
In Windows XP, click the Start button or press Windows Key on your keyboard and choose Control Panel. Windows Vista, 7, 8 and 8.1 users, move down here.Click here to show or hide instructions for Windows XP
Click Add or Remove Programs. First picture is for users of Control Panel in Category View, the second one for users of Control Panel in Classic View.
Find your current antivirus program, click on its name and then click Change/Remove or Remove button (button name depends on your antivirus program). Then follow the uninstall wizard to remove the program. You probably have to restart your computer after this. You will also see Security Center's red shield icon in Taskbar Notification area, this is normal because you have temporarily no antivirus program installed.
Now move to downloading part.
In Windows Vista or 7, click Start button or press Windows Key on your keyboard to open Start menu. Then type "remove" into Start menu Search box and click Add or remove programs. If you have Windows XP installed, check instructions above.
In Windows 8 and 8.1, open Settings Search using keyboard shortcut Windows Key+Q, type "uninstall" into Search box and then click Uninstall a program. Alternatively, use keyboard shortcut Windows Key+X to open Quick Links menu (a list of system tools) and click Programs and Features.
Find the antivirus program you want to remove, right-click on it and then click Uninstall or Uninstall/Change (depending on the options your antivirus program provides). Then follow the uninstall wizard to remove the program. You probably have to restart your computer after this. You will also see Action Center flag icon with red cross in Taskbar Notification area, this is normal because you have temporarily no antivirus program installed.
In case you have an older version of avast! Free Antivirus installed already, use the simpler and faster upgrade process instead.
If not, go to avast! home page and click Download button in the avast! Free Antivirus column on the left.
In case avast! offers something to buy, click No thanks, I want free protection.
You will be taken to CNet's Download.com page. Click the green Download Now button.
After downloading, launch the setup program if it did not start automatically.
This is very important: In the Welcome to avast! dialog, clear both Yes, install Google Chrome as my default browser and Yes, install Google Toolbar for Internet Explorer check boxes. While neither of these products is malicious, it is never recommended to add programs or toolbars that you do not require.
Then click the large blue Regular installation button.
Next, avast! Free Antivirus Setup reminds you that some personal information is gathered, but it will never be used to identify you, or shared with third parties. Click Continue.
Installation starts with creating a System Restore point and downloading updates. This might take some time. Just stand by - after this the program will be installed.
After the installation is complete, click Done. A quick startup scan will be performed automatically.
This completes the downloading and installing part. Read about configuring avast! Free Antivirus next.
In case you get errors during installing or upgrading, such as "Setup GUI was not initialized successfully" and "You are trying to use an old version of the avast setup", please verify that you do not have any other anti-virus programs or tools (especially those by McAfee and Symantec or Norton) installed. If you do, uninstall those and try again.
Also, make sure you've downloaded the latest version from avast! Free Antivirus download page. The setup file does get updated from time to time.
If you have no other anti-virus programs running, download avast! Cleaner to your Desktop (or some other folder) and start Windows in Safe Mode. Run the downloaded program to clear all avast! files and settings that might cause conflicts and errors. Restart your computer, let Windows start normally and try running avast! Free Antivirus setup again.
When something else seems to be blocking the installation, run RKill to terminate malware processes and services that might interfere with downloading or installing avast! Free Antivirus. Then retry the installation again, without rebooting your PC.
In case you have an older version of avast! Free Antivirus installed already, open the program by clicking its orange ball-shaped icon in Taskbar Notification area (aka System Tray).
Open Maintenance tab. Then click Update Program.
Wait until avast! downloads and installs the updated files. This might take several minutes, but this will certainly be much quicker than downloading and installing the whole setup package.
After the latest version has been installed, you will probably have to restart your computer. Click Yes in the dialog.
After the reboot, an overview of new and improved features appears. Click Continue.