In our work we often come up with a question like how does a virus will affect your computer performance? Viruses carry a lot of negative effects for a computer and these effects can even lead to a crash down of the entire system of a computer thus leaving it useless for future use.Virus infections can be termed as one of most dangerous situations regarding computers and in business sector it can be considered as a nightmare. Viruses are the most threatening and most feared aspect in cyber world and there are numerous reasons to this.One of the effects of a virus on computer performance can be realized when a file that you have tried to open has stopped responding to your mouse clicks? There cannot be an obvious and apparent reason for not opening up of the file that had been saved correctly by the user, but a computer professional will definitely come to know that this is a result of virus infection in computer and it will not work until the system has been cleaned up from the virus infection.A virus affects the computer in many other ways and the extent of damage to the computer depends upon the type of virus that a computer has been infected with. Once talking of the basic virus and their effects, we must bear in mind that foremost effect on computer is its reduced performance. Viruses infect program files of the computer which in turn cause a missing link while the computer tries to operate.At times data on the systems starts disappearing and it causes extreme danger for the user personal information. A User will feel helpless in such a situation until and unless he looks for a reliable antivirus. System free memory is reduced by the virus thus leaving the system with very less operating resources. It can also happen that the user is even unable to delete old data or store some new data on his system.Those who maintain their important official work on their systems and do not keep a proper back up with them must remain very much vigilant for any signs of an infected file. This is a huge risk and it demands that the user must get his files and data protected by using a registered antivirus.Mostly we come across a situation of getting wrong properties of a file or folder. The file has been infected by the virus and it will not open up the data unless it is cleaned from the virus.How does a virus will affect your computer performance is dependent on the kind of virus that has infected the system and precautionary measures that have been taken by the user. There is no virus that cannot be treated but it requires a well developed antivirus to be active and ready to identify infected files attacking the system.