If your computer is connected to the internet, not directly, but through a router or server, then there is a small probability that it will be infected directly from the internet. For example, by opening a communication port. This is why, not using the mobile internet USB dongle is a good way to avoid infections.
A good antivirus choice depends on the current taste. All antivirus software is now good and some even too high of security. Some antivirus programs prevent downloading any file from the internet. Personally, I prefer Avira Antivirus because it is intuitive and does not overload the system as other antivirus programs do. My one recommendation is not to use two antivirus programs or antivirus software and a firewall from two different companies, as they will most likely interfere and ruin the system.
The best software today to clean the infected system is Malware Bytes. This system is free to try and includes all the features enabled, except for the real time protection which is disabled. But in order to for clean the system, there is no need to have real time protection. This system is good for minor infections. Some viruses avoid Malware Bytes completely. This might be because virus creators tested the virus and made it invisible to this specific software. If I wrote a virus, I would test it with all the possible antivirus software programs just to make sure that it goes through.
It is recommended to boot the infected system as usual, and then run Malware Bytes. If this is not possible, boot the computer to Safe Mode, run it and Malware Bytes will do the best it can. If it scanned the infected hard drive as an external hard disk, it will not do as good a job as possible.
How to get data from an infected system that does not boot to Windows. One way to do this is to remove the hard drive and connect it to another system as an external hard drive. But, personally, I would not do this as the system infected with a virus can pass easily the infection on to another system. The best way to do this if you want to be 100% safe is to boot the system from a bootable live CD or DVD like Ubuntu, and to take all the data to the external hard drive. Or, another option is to use a Mac OS X to get the data back. A Mac OS X is immune to Windows viruses.
There is also another tool that works on some occasions. This tool is Windows Restore. Unless there is no hardware fault, Windows Restore will provide good results. This also depends on how severe the virus infection is.
You can get a good antivirus Avira by clicking on the image below.
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