Will Complete PC restore clobber itself?

I was running Vista on C: and had a complete backup on D:

I tried to setup a RAID array using a SIIG card (that's another story) and
ended up with a corrupt C: I went back to the install disk and tried to
restore, but whenever C: was in the system I got the error "Can't get system
information from disks". So I removed it completely and tried the restore
with just D: (now C

So now rebooting the install disk it recognizes the restore data and will
let me restore C: to C: but with the warning "This will reformat and erase
all data on C:".

I didn't risk it and opted for a clean install. I'll try to recover the
original later. But I wonder, would it really reformat the partition the
restore data is on and clobber the backup?