Replace all the files manually.
Go to:
www.magellangps.comsupport
search for the latest version 4.86
download it and save it in a folder
change Magellan_Maestro_4250_4_86_Rel1.exe TO Magellan_Maestro_4250_4_86_Rel1.ZIP
now, unzip Magellan_Maestro_4250_4_86_Rel1.ZIP to see the files.
you may need to drag & drop these files by hand onto the Magellen hard drive.
To see the files on your Magellan, plug it into your computer with a USB, and open the folder.
Lastly, try to run the update; double click on Setup.exe in folder
Magellan_Maestro_4250_4_86_Rel1
to see if it will then do all file updates for you, in case you missed any.
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FROM ANOTHER THREAD:
I followed your directions above, and changed .exe to .zip: Magellan_Maestro_4250_4_86_Rel1.exe TO Magellan_Maestro_4250_4_86_Rel1.ZIP.
Then, I was able to unzip the files to see them. Then, I manually dragged all the exe files and all the dll files (i didn't bother with .bmp, .xml, or sound files). I had trouble with the file IVTDialorStrResChs.dll, and had to re-do this file and some others because I got a "file corrupt, can't copy" message. The second time, I got these to copy over.
After all this, I re-booted the Magellan. Then, I pluged it back into the computer using the USB so I could see the files again.
NOW, I ran Setup.exe by double clicking on this file in the open folder on my desktop (this is one of the files I unzipped under folder Magellan_Maestro_4250_4_86_Rel1).
It ran! I didn't need to be on the maps screen on the Magellan. Somehow, the file copies I did helped. This fixed the problem, I could see my home screen again Yeah!
The customer service guy at Magellen told me to download the lateset update, and to do it manually, if I could. At first, he tried to get me to spend $200 on a new Magellan!!