Firstly, some ideas/hints/tweaks/links:

• FZ5 Ticks and Trips page from the ever-inventive Seemolf.
• Seemolf's post with his inventions!
• Panasonic DMC-FZ5 Adapter Modification Utilizing a Raynox rt5264p aluminum tube adapter to get filters and converters closer to the FZ5 lens.
• Changing the Panasonic Lumix DMC-FZx Picture Counter
• ISO1600 tweak for every LUMIX
• Dedicated FZ30 site - some stuff here applies to all FZ series
• FZ30 User Guide - excellent resource for add-on wide-angle and teleconverter lenses for all Lumix FZ series

Panasonic's Tatsujin adjustment software

Panasonic Canada made available for download some Lumix adjustment software for Windows PCs called 'Tatsujin' ('master' or 'expert' in Japanese) that connects using a special USB driver, PV-DC3000, for DMC-FZ4/FZ5, for the DMC-FZ30 and for DMC-FZ3/FZ20.

There is a certain amount you can do with the software without connecting your camera, plus a lot of interesting documentation, in mangled English, to read. There's also some keypress sequences to try on the camera to ready it for using with the software and resetting it afterwards. If, after reading all that, you still want to connect your camera, make sure you don't write any EEPROM data to the camera or adjust anything.

Here's three links to discussion of Tatsujin from DPReview Panasonic forum.

After running the installer, the 'C:\Program Files\WinTatsujin\Dsc\FZ4PP' directory is created containing FZ4.exe, or the 'C:\Program Files\WinTatsujin\Dsc\FZ30PP' directory is created containing FZ30.exe, or 'C:\Program Files\WinTatsujin\Dsc\FZ3SR' directory containing FZ3.exe (for the dmc-fz3-fz20.exe package).

• In the Help subdirectory of each is a manual called 'HowTo.pdf'. In there is how to set up and use the software to adjust all camera settings after manufacture/repair. Read it carefully.
• In the 'Adjust\Cam\Usage' directory, there's another pdf, Usage.Pdf, detailing how to connect the camera for adjustment. Read it carefully, too.

The only option that looks un-dangerous is this 'Each mode', accessed from the 'Operation' menu, 'Outside control' option, which seems to allow remote operation of the camera.

The rest of the menu options will probably kill your camera - you have been warned!

You can run the software in demo mode without the camera connected, by holding down [Shift] while clicking on [Connect]. Or, as the HowTo puts it:

Here's a screen grab of the 'Each mode' dialog, accessed from the 'Operation' menu, 'Outside control' option.

Connecting camera with PV-DC3000 USB drivers

To set up the camera for service connection by USB, you have to make your PC use the new USB drivers from the '\Program Files\WinTatsujin\Dsc\FZ30PP\Driver' directory, Mkeusb01.inf and Mkeusb01.sys. Here's a string from the former:

VendorName="Matsushita-Kotobuki Electronics Ind.,Ltd."
DeviceDesc="Panasonic PV-DC3000 USB Driver"

So, when you connect your camera to your PC, if it is detected as a USB mass storage device, you'll have to uninstall that and install the PV-DC3000 driver instead.

As well, a special keypress sequence has to be made on the FZ5 to set it up for connection in Service Mode, and to set it back again to the initial setting. In my experience, if these don't work at first, keep trying them, perhaps a bit faster.

While it is recommended to use a power adapter, this is probably only a precaution to avoid powering down in the middle of setting the camera. Make sure you have a fully charged battery, and you should be OK.
From FZ4/FZ5 Usage.pdf, page 2, Step 4:

• How to release initial settings and change into service mode
  1. Set the mode dial into [P] mode.
  2. Turn the [Power SW] on, while pressing [OIS] and [UP arrow] simultaneously.
  3. Set the mode dial into [Playback] mode.
  4. Press [OIS] and [UP arrow] simultaneously. If you have beeps turned on, you will hear a beep sound, to show that the camera Initial setting has been released.
  5. Turn the [Power SW] off. If the warning mark " ! " in a yellow triangle is displayed on LCD monitor, then it has worked.
     If not, repeat the steps from the beginning.

To put the camera back into normal/initial mode AND reset all user settings to default (time included) , follow this sequence.
From FZ4/FZ5 Usage.pdf, page 4, Step 7:

• How to release service mode and return to initial settings
  
  1. Turn the [Power SW] on.
  2. Set the mode dial into [P] mode.
  3. Turn the [Power SW] off pressing and holding [OIS] and [RIGHT] simultaneously.
     After that, the 2-page menu below appears on LCD.
     
  4. You can [Select] with the [UP] and [DOWN] arrows, [Set] with the [RIGHT] arrow, or [Exit] with no changes by pressing the [MENU] key.
     After selecting the area name using [UP/DOWN] , press [RIGHT]. Beware! You must choose your correct area code or you will kill your camera! Known area codes are listed below.
  5. The final confirmation screen appears with "Initial settings", your chosen area code, "OK, Cancel [LEFT], End [RIGHT]". Press press [RIGHT] and initial setting will be completed and power will go off.