Not sure answering my own question is sound but this appears to be fixed by using windows eplorer/drive manager to change the ext USB drive's default drive letter and re-formatting the blank drive under windows. The Dell software then seemed to properly recognise the ext driveand make it available as the destination for the rescue backups. Noted that the Dell software created a new 500MB partition for a bootable system backup leaving the rest of the orginal partition to store user backups. Lesson learned - consider reformatting a new ext drive using windows before saving/using the drive.
Hi  Previously posted to Win8 forum in error -  sorry. After using pre installed basic version to do factory and drivers backup to two USB sticks,I just upgraded to Premium. My XPS Win8.1 recognises my new empty Usb3 drie (1TB primary NTFS) Dell BandR allows me to select the USB drive as backup destination, but on starting to create a rescue disk, the 'drive initialization' phase always fails with an 'error initializing drive' would appreciate any advice on how to fix this. Thanks Paul Kelley
Dell Bkup & Recov Premium fails to initialize ext USB drive