Having created a Steam backup under Windows Vista (took the best part
of four hours, but I didn't really want to have to download >50GB of
data unnecessarily), I attempted to restore from the backup. First of
all, I saw a sliver of a window appear, with the title 'Restore Bac',
and the Steam process started running full speed on one CPU.
Eventually, a window appears asking me which games I'd like to restore
from backup, so I select them all and continue. Next thing I know,
Steam has merrily started downloading all the games over my broadband
connection again. Not so useful.