I had this problem and solved it with some help from a friend.
you need an IDE cable adaptor to connect your desktop pc HD to a laptop HD, (got 1 for £5 of ebay). take the HD out of your xclef and connect it to your pc using the adaptor, dont disconect your desktop HD. boot up your pc, go START-MYCOMPUTER, there you will see the xclef HD, right click on it open PROPERTIES-TOOLS and CHECK NOW on the error checking, this will repair the errors, you then need to go to START-MYCOMPUTER open the xclef HD find the folder "firmware" and delet it, create a new folder and name it firmware. download the pevious version firmware to the one you upgraded too, i downgraded to 1.099, copy BOTH firmware files into your new firmware folder that youve just created. put your xclef HD back in its case and start it up.
we spent a good 8 hours figuring out how to do it and the instructions above was the way we it, ive tried to make it as simple as possible, but its not that hard anyway.
i got the problem when doing a firmware upgrade from 1.099 to 5.307 and it wasnt my upgrading that was to fault its xclefs firmware 5.307 ive tired several times to upgrade to it but everytime the same problem, it wont boot up afterwards, not until i went back to the 1.099 version, so unless theyve brought out a new one i wouldnt touch it
hope this helps,

I have a contact at Xclef, he's been very helpful to me with a problem I had with the firmware upgrades:
Martin Kim: martinkys@xclef.com
That email address was good as of 12/07/04.
Good luck getting yours fully operational--I love mine and don't regret the purchase at all.
Kelly.

Hmm finally I solved the problem of the freezing up on start... i tried a few firmwares but it didn't work untill I reinstalled v1.072. I connected the xclef to my pc, while hooked up to the adapter for power, deleted the existing firmware, and put the v1.072 in the map firmware, than disconnected the usb.. Started the xclef with the power adapter still in it, it upgraded the frimware, restarted and.. It worked.. Now I'm gonna reupgrade it to a higher version, but not the highest, don't wanna push my luck.. (sorry for my english, its not my own language..)
PS got the firmware from http://openjukebox.free.fr/download.php?list.3, strange that xclef don't have it on their website, but then again there not the best company around.. No more xclef for me the next time around

I too had the same problem, after trying to update only the logo came up and it froze when trying to boot. I didn't need to open up my Xclef though, I downloaded the two files of version 1.099 from http://openjukebox.free.fr/download.php?view.36 and simply put them in my FIRMWARE folder on my Xclef as I could still get to see and change the files on my Xclef via the USB cable. After that it updated / downgraded the firmware and it worked!
Thanks for everyone's help on this board!

Any business in or near Edinburgh who will repair my out-of-warranty Xclef HD500?

hi im another lover of my Xclef 500 to fix this problem of freezing on step 8 of the start up just copy this file http://www.members.westnet.com.au/kerryn21/HD500_MODEL_5118.bin
into the firmware file of your xclef and turn it on it will install version 5.118 i had the same problem a few montths ago but i thoughtthey would have fixed it bye now

Has anyone had this problem - mine seems to have completely died! It wont charge and it wont switch on at all - Im not sure where to go from here, as unlike a lot of these other problems, I wasnt trying to upgrade anything, just add some tunes, which it had done successfully but I unplugged everything and then there was nothing when I went to use it! Any help would be very much appreciated.

Its easy to fix, no need to mess about with taking apart your xclef and connecting it directly to your laptop. It will still connect via usb, espically if you are running windows XP. Just connect the xcelf via USB to your laptop, download : v1.099 v1 (SysFile v1.099) from http://openjukebox.free.fr/download.php?list.3
go to 'my computer' and the 'XCLEF' drive so you can see all the files on your xclef. Find the FIRMWARE folder, go into it, delete all files (should only really be one). Extract the firmware you downloaded, copy BOTH files into the FIRMWARE folder on your xclef. Then turn off the xclef and then back on (it will 'update' itself), and just by magic it works again!!

Go to www.xclef.com and follow the instructions for the latest firmware, I had the same problem initialy but on carefully reading the instructions I managed to upgrade to 5.307

Hi guys, try and sort this one
when I try to boot the Xclef HD500 it starts to boot and then comes up 'NOT FORMATTED' and switches off again! have connected to the pc via USB and all my music and all the other files have gone! HELP!
stevesevenstars@aol.com