It would be great if we could specify what folder gets used for the temporary cache while Retrospect is running. Currently, at least under Win2008, it uses C:\ProgramData\Retrospect\...{etc}. Support has said that you need to have 10GB free per concurrent execution running that is doing a system state backup; though my experience is that it needs to be more like 15GB. Though 15GB doesn't seem like much, sometimes the free space available on a C: of a server is kept to a minimum to avoid wasting free space.
I would like to be able to tell Retrospect to use the D: or E: drive.
