UPDATE: Apparently the drivers can be auto updated if you have an internet connection and you have Windows 7 set to pull drivers from the internet. The following directions would still work for a computer not connected to the internet.
Warning: These instructions are not endorsed by Metz. Proceed at your own risk.
The first step is to download the Metz update for your system from Metz: Metz 58 Firmware Update.
or Metz 48 Firmware Update
After that has completed, open the Windows executable.
Type the desired location and click "Unzip"
The screen should pop up with a confirmation:
Click OK and remove the batteries from your Metz flash and turn it off. Attach it to your computers' USB port using a mini USB cable. Windows will pop up with a message saying it found an unrecognized device.
An error pops up saying the device driver was not successfully installed, click here for details. This is where the instructions differ significantly from what Metz provides for Windows XP or 2000.
Go to "Start"-> "Control Panels"
Click View Devices and Printers
You will see a warning symbol under a device called "MB58 AF1 Pentax"
Double click on the device and click the "hardware" tab.
Make sure the device is highlighted and click "Properties".
Click "Change Settings".
Click "Update Driver"
Click "Browse My Computer for driver software"
Browse to the files you just unzipped, in the sub directory "58AF1 Pentax V1.1 GB\Driver"
It should say it is installing device and it was successfully installed, but there is a second device that needs to be installed as well.
Close ALL windows. I found I must close the control panel for view devices and printers or information wouldn't refresh correctly.
Open the Control Panel, open the View Devices and Printers control panel again. In the View Devices and Printers window, double click on the MB58 AF1 Pentax device again:
It still has a warning symbol on part of the device
Highlight the device with the warning, and click Properties (it doesn't show on mine as I can't do a fresh install since I already installed it once).
Repeat the procedure above for the second device with the warning. Click on "Properties", and then click on "Change Settings" and then on the "Driver" Tab click "Update Driver" and browse to that same folder you did for the first part.
After the driver install is complete run the file:
In the C:\Users\Eric\AppData\Local\Temp\58AF1 Pentax V1.1 GB\FirmwareUpdateGB.exe
(where ever you unzipped the files, in the folder \58AF1 Pentax V1.1 GB\)
After that there is a two part process. Downloading the data and updating the flash. It might take 1 minute total. Halfway through a window pops up saying "All datas are download successfully". The bad grammar adds to the experience :) Wait a minute or two to be safe once everything is done and unplug the flash. Put the batteries back in and start it. It should say version 1.1 when it boots.
I hope that helps someone!