How did you include System.Drawing.dll - did you right click on your project and use add reference to add a reference to the System.Drawing assembly?
System.Drawing.Image.FromFile is declared as
public static Image FromFile(
string filename
)
so, as far as I can tell, your code should compile ...
You are not creating an instance of the Image class in your code, that happens somewhere inside FromFile.
Regards
Espen Harlinn