As firepa63 stated above, There is two versions of the Nav because of the MFD ver 4 analog ver 5 digital
I had an 05 Nav disk .04.2 Version gen 4 nav analog same as yours
I traded up to 07 nav disk .06.1 version gen 5 nav digital
I just updated my nav disk in May to .07.1 version paid 250 dealer salesman stated price increase to 290 as of now.
They do have an .07.1 ver disk for the gen 4 your nav that the one you need here is the part #v.07.1 DVD (86271-33047)
Make sure your dealer orders the correct disk
Here is the numbers on the disk
Here is a link from Prius Chat read the entire thread its several pages to get the right part number
and more info see post #1 and 37 and third party sources for the disk look around for best prices
http://priuschat.com/forums/audio-elect ... -dvds.html
Also on the gen 4 nav only there is a manual override to disable keyboard lockout of nav while car is in motion getting to the service screen
putting the new .07.1 disk may permanently disable that feature there may be a way to use a file loading.kwi on your present disk so keep your old disk.
google lexus nav disable
There is a procedure to burn a hybrid disk. replacing the new loading.kwi on the new disk replacing it with the file on your old disk. Use a dual layer DVD NOT A SINGLE LAYER when making the disk in ISO format
If you don't care about the above paragraph just have the dealer install the disk and don't forget to reset the map region & Time Zone after the install.
The map version .04.2 stood for 2004,.07.1 for 2007.
Hope this helps