How to make your computer safe from virus?

Ok.Here is the funny part.A couple days ago.My friend tell me to look at his computer why is it slow.After I search for a couple of minute in his folder.I found Svichost.exe in one of his shared folder.I do the same thing for my computer to remove the virus.When I install hijcakthis and check the symptoms for that virus.

But there is no show that the computer is attacked by the virus.Weird isnt it.After I ask him where he install his OS(Windows).He said that he install it in other partition(D:\).So I conclude that if you want to save from virus dont install your OS in C:\.Install it else where coz usually it virus will attacked your system on C:\.(Not all virus)

****Info about Svichost.exe(New Folder.exe)
-It disable your task manager,regedit and folder option.So becareful.Dont just click a folder.