I have wanted a GPS for quite awhile now, and when I saw the MyGuide 3000 GO on sale at Fry's it was hard to pass up.  It was even more tempting when there was a return unit for another $50 off the discount price.  Yes the OS is a bit aged (Windows CE 4.2) and there is no USB port, but it does have a 400Mhz ARM processor, 64MB of memory and 32MB FLASH (which I figured would be all dedicated to ROM anyways. 

After playing with the system for a little while after getting it home I came across a few rather annoying bugs that wouldn't seem to go away:

The positive elements that made me want to work on these problems rather than just take it back:

Disclaimer:  Before you try changing anything on you GPS, remember that anything you do could possibly render the device useless, especially if you are not careful about READING these directions and then FOLLOWING THEM in the correct order.  The details mentioned here have worked for me but may have very different results for you.  Whether you do or not follow these directions I will not be held responsible for any damage you cause to your own system.

Digging Around

I started with looking at the contents of the SD card which contains all the maps.  It also contains a few other folders which contain things that make hacking the unit a little easier.  Via my PocketPC I copied the entire SD card to my local computer so I could view and edit any of the files on it:

You see a text file here named ADDONS.TXT.  Opening this reviews a rather simple menu structure which controls what is displayed on the menu when the card is inserted:

Well it looks like that is where the "Mutimedia" typo is coming from, but that doesn't make any sense since it still appears when the SD Card isn't inserted in the device.  As an experiment I went ahead and fixed the typo, overwrote the file on the SD Card and rebooted with it inserted.  Guess what?  Nothing happened (as expected).  So the flash disk folder doesn't do much (as I said earlier).

The DATA.ZIP file is really a zip file which contains a bunch of graphics and files for the menu system.  Nothing super-exciting there.

We'll peek in the MyGuide folder later.

Seeing what's on the internal system

Note: You can skip this step, especially if you don't have a PocketPC and use the included Windows Explorer.  Click here to skip down to the next section.

Now knowing that we have a way to add and remove items from the menu that appears at startup and knowing the underlying system is a PocketPC already, all we need to do is find a file explorer that operates in this environment, add it to ANOTHER SD Card, and edit the menu file appropriately to give us the ability to start this program.  A Google search for "PocketPC file explorer" yields many results.  I decided on a program called Pocket Explorer since it promised a Windows-like interface and is compiled for ARM.  I installed this on my regular PocketPC via the installer and then copied the executable to a 64MB SD Card (whether you can get the executable in another way without installing on a real PocketPC I'm not sure.  It's probably not hard to do though).  I also created a ADDONS.TXT file that I copied to the root of the SD Card:

Putting this card in the GPS I was pleasantly greeted with my new menu (this screenshot was taken after I fixed the Multimedia option):

Choosing my Explore application I am presented with the internal filesystem:

You can now see the internal Flash Disk folder from which the menu and navigation system is booting from.  Notice many items are in German.  If you don't know German (I don't either) you should proceed with EXTREME CAUTION.  Babelfish is your friend in this case.  If you don't know what something says, use Babelfish to figure it out first.

What I've figured out:

Eigenschaften = Properties
Ausschneiden = Cut
Kopieren = Copy
Einfugen = Paste
Loschen = Delete! DO NOT FORGET THIS ONE! Normally you won't want to click on this!
 

Scrolling down and exploring the Windows folder reveals the Explorer.exe is still available:

Skipping the Pocket Explorer step (if you don't have a PocketPC)
This is probably the better way to go anyways.  Since you know the directory to Windows Explorer, you can instead create a new ADDONS.TXT file pointing directly to this application:

This brings up the standard Windows file explorer.  The last menu item should be the control panel link:

Some things are useful here and some aren't.  You need to understand that some (most) PocketPC settings are stored typically in the RAM of the device which is erased when the device loses full battery power.  The way this GPS is assembled it seems that the on/off button either by accident or by poor engineering actually doesn't keep power available to the RAM while the device is powered off.  Thus any settings the OS puts in the RAM are lost when you power it off.  The most annoying of these is the time and date since we are bothered with this every time the unit turns on.

The control panel:

Most useful here is Datum/Uh... = Date and Time Zone.  You can set a Date and Time which the system will forget the next time it is powered off, but at least for me it stopped hounding me for a date and time when I turned the unit on after I did this.

Possibly also due to setting a language in Landereins... has caused the language menu to stop appearing all the time (or this may be due to freeing some room on the full flash disk as I explain later).
 

Fixing the Multimedia Typo

Shown here is the Flash Disk folder:

The IGOPATH.TXT file is the same menu file that we messed with on the SD Card in the flash disk folder.  To be safe I copied this file to my SD Card and then to my PC.  I edited it to look like this:

I then put it back on the SD Card, used the file explorer to again get to the Windows file explorer (I've had more luck copying files using the Windows Explorer instead of Pocket Explorer).  I made a backup of the original IGOPATH.TXT elsewhere on my SD Card, then copied the changed file over.  Now when I boot I don't have to look at Mutimedia anymore.

You should also have a SettingsBackup.ini file in this folder as shown above (SettingsBa...).  If not then your Flash Disk is probably out of free space, and is probably really why your system keeps asking you for a language and time set every time it boots.  I'll show you what you can safely remove next to make a bit of breathing room.

Making some room on the Flash Disk

I'll add more details later, but you can safely remove the demo mp3 file, video, and image file that each of the multimedia viewers use.  They are found in:

//Flash Disk//XImage//
//Flash Disk//XMovie//
//Flash Disk//XMP3//

Unfortunately I don't remember each file's name since I deleted them and didn't make a backup.  It is pretty obvious which file they are in each folder though (I believe they were named demo or example or something of that sort).

After all three of these files are removed that should free about 700KB or so, which gives some breathing room for settings files that both the menu system and MyGuide want to store on the flash disk.  Data backups in MyGuide were also failing prior to doing this, now they work fine.

Technically if you don't plan on ever using the Multimedia features you could remove the applications completely (maybe after making a backup via a SD Card copy) and removing the Multimedia section from the menu.  This would give you a couple MB free (what you need it for I'm not sure).

FAQ
I'll add responses to emails I get here as I have time.

Q: I don't have a PocketPC and I can't get a copy of Pocket Explorer to put on my SD card.  Can you supply one to me?
A: Pocket Explorer is listed as freeware, but if you visit the author's website (http://www.citadeldevelopment.com/) you find that the license does not allow it to be redistributed in this way.  Fortunately you don't really need this step anyways as you can use Windows Explorer by creating a link to it directly in your ADDONS.TXT file.  The location is "\\Windows\\Explorer.exe".  I have also added this information to the tutorial above.

Q: I want maps for somewhere other than the US.  Where do I get these and how do I make them work?
A: I don't have maps for anywhere other than those provided, and I don't know how difficult it is to get get maps for other countries.  If you do obtain them I don't know what is needed to make them work.  From what I've read elsewhere the application looks for the specific SD card that is provided (probably by a manufacturer's ID or some unique tag in the SD Card's registers) to verify the software.  The underlying application is called I-GO (http://www.i-go.com/en/) where you may be able to purchase a SD card for the country you are looking for.  Since you do have the option of using any PDA-based navigation software you could also find another application that suits your needs and install that on another SD card.