If the virus is in a file and you have a clean copy of the file somewhere else, then delete the virus-infected file. This is always the safest. If you don't want to delete the file or if the virus infection is somewhere else, use a disinfecting program to remove the virus. Removing the virus doesn't guarantee that the original file or disk will be okay. Some viruses damage or overwrite information that cannot be restored.
Viruses spread quickly and can cause a lot of damage.
In addition to the risk of overwritten data, some viruses also do other damaging things. For example, they can overwrite data on the hard drive, damage the partition table, take away the available memory, or slow down the system. If the virus is not removed, it will cause you trouble in one way or another and will spread and cause problems for many other people. For the PC there are many commercial and non-commercial software programs to choose from. It can scan computer memory, boot sectors, and files for known viruses.