VS 2008 - Unzipping Files From Program (Shell32 Functionality)

I want to unzip files from my program, so i'm using the Shell32 functionality like so:

Module Module1
Sub Main()
Dim sc As New Shell32.Shell
Dim srcDir As Shell32.Folder = sc.NameSpace("zippath")
Dim destDir As Shell32.Folder = sc.NameSpace("destinationpath")
Dim items As Shell32.FolderItems = srcDir.Items()
destDir.CopyHere(items, 256)
End Sub
End Module

This theoretically works, but i'm unzipping an 8Gb compressed file and the dialog that pops up says it will be done in 1day, 19hours. This is ridiculous because when I just right click on the file and decompress it from there, it takes only a couple of minutes! I can't imagine what the problem is! I know that the shell process actually spawns its own thread, so I worried at first that my process was exiting before the thread could spawn and added a Thread.Sleep(1000) after destDir.CopyHere() but it had no effect.