OK, I have downloaded from Windows Live Spaces (don't know if this is useful, but might be) a .CAB file containing an Index.XML file and package.cab, package01.cab through to package12.cab.
The index.XML simply has names of all the subsequent package.cab files and their offsets. The first package.cab has a single 26MB XML file which appears to be an OfflineSyncFile definition which I am guessing is the meta data for all the other packageXX.cab files.
Now the question I have is how should i be going about extracting these things and piecing it all back together again.
I have tried WinRAR, which extracts all 800MB for me into unnamed files and randomly named directories. I have also tried the standard extract in Windows Explorer with much the same resusts.