After an unschedule power cut the voicemail has stopped working I believe the system was off for a few hours, the programming is still there. No voice mailbox can be accessed and the delayed foward of the main number to voicemail no longer kicks In. Is there a way to to restart Vmail ??

I would reseat the media card. This can be done at anytime and it does not drop calls or anything.

If the system cannot read the media card, you will get this. Pop it out and back in and retest. Okay to do during the day.

If it is a 7100 and the VM is embedded, there is not a way to reboot it without rebooting the system. I would just call the customer and tell them you're going to reboot it and it takes 4 and a half minutes to come back up and go to System Control / Commands / Reset and change System Reset to Reset and Save and do it there.

I have been to system control/commands/Pre-install Reset and only have option to Reset or memory clear,does the reset leave the system programming as it was??

A system reset will only restart the system, it won't wipe the programming, but if you want to be safe then take a backup of the programming prior to restarting it