I have been burning avi files to DVD with no problem and speed was good. The DVD burner is listed as HL-DT-ST DVD-RAM GH10L and I'm using Roxio Easy Media Creator 10 with Windows Vista.
Now the burning speed has dropped to about 10 hours to burn one DVD. The only thing I have done is install Microsoft .net framework 3.5 SP1. I have since unistalled it and also did a system restore but no luck fixing the speed problem. I have also uninstalled the Roxio program and reinstalled it.