During upgrade of map 1900.20 (8Gb) application crashed now device does not start

During the update of new card material the power too the computer failed so did the update fail.

now during boot it does not continue.

did try the following but no results:

1) keep power button and lthe lap button touched and plugin Garmin Expres. When splatch screen ‘Garmin’ shows unselect power button. After some seconds device shows USB mass storage device but computer says disk is not formated correct.

2) select all 3 buttons so it boot. Unfortunately not the result i need.

I was hoping I could get the mass usb drive so I could remove the corrupted map or copy an other map.

please advice how to get my device working again.