Hi Gavin
Dragging this one up from the depths, I can tell you I had the same problem with my 57 plate Le Mans running 5570 software. Seems the HDD needs to be formatted FAT32, which my Windows 7 PC wouldn't read. I made the mistake of formatting again, I assume it did it NTFS.
Either way, re-formatting it again FAT32 got it working. I used my Linux box, but an old PC would do it. I also assume there is a patch somewhere to make Win7 work.
Good luck with it. BTW, if you want a set of 5570 discs, mine are now surplus to requirements. They're CDR's, but they upgraded my car just fine. Just cover the P&P and they're yours.
Cheers, Chris