If you get stuck PM me direct.
Use imgburn or similar (
http://www.imgburn.com/index.php?act=download) to burn a new
(blank) cd with the new downloaded firmware image.
Download, unzip the v29 image and then open imgburn, and select the "write image file to disc" then select the v29.mds (i think) file.
Select the write speed as x1 (or the slowest rated speed for the disc, you
must do this) and then burn on a good quality cd.
When its finished writing your new firmware cd,
Goto the car open the drivers door,
Goto the nav computer and press eject on drive,
Eject the map disc,
Switch ign to pos 1, leave door open.
Insert firmware disc into drive, follow instruction on nav screen.
Wait (approx 6 mins) till sat nav asks to eject cd and reboot.
Eject cd,
Confirm reboot.
That's it.
Do not switch off ignition or close the door when doing the upgrade.
BTW, is your drive a MK3 or a MK4?