VBScript runs in client side and you are trying to get the server path
May be you can try some thing like below
<script language="vbscript">
dim path
path = "<%=Request.PhysicalApplicationPath %>"
alert(path)
</script>
If you trying to use vbScript in an ASP/ASP.NET page, then you try using Server.MapPath as well.
<%=Server.MapPath("your file name")%>
edit ---
Seems like in your case you are interested in finding the mapped drives of the user that is logged in. You could something like:
Set objNetwork = WScript.CreateObject("WScript.Network")
Set colDrives = objNetwork.EnumNetworkDrives
For i = 0 to colDrives.Count-1 Step 2
Wscript.Echo colDrives.Item(i) & vbTab & colDrives.Item (i + 1)
Next