A Hard Drive is a media storage device which is built into the computer tower or laptop and serves as a storage space for the Operating System, program files and other data like photos and documents
 A Hard Drive
You can think of a hard drive as a container that holds the Operating System, program files and all the other data that is stored on the computer.  
 An Empty Hard Drive
A hard drive can not prevent the user from storing data and it also can not stop viruses from infecting it.  
 Hard Drive containing data
A hard drive infected by a virus
In the past viruses used to be simple programs that were removed using simple tools 
 Virus being removed
 Virus removed from Hard Drive
A virus infecting a Hard Drive
Viruses today are complex programs that can outwit the smartest operating system. Their behavior is similar to a drop of ink into a container full of water. 
  Infected Hard Drive
Viruses can also outsmart anti virus tools by "hiding" in restricted areas such as System Restore or registry, system files or Java scripts. Therefore they are not easily detected by anti virus programs or Registry editors 
  Anti virus programs may not always work
Some viruses may remain on your hard drive even after anti-virus programs remove obvious viruses 
 Viruses still present
The guaranteed removal method is by reformatting the hard drive then reinstalling the Operating System then reinstalling programs and tools OR 
utilize AltE, the AltErnative to PC solutions.