Need help devising a plan for backing up Windows 7

[traptor87]

Hello,

My boss and I need to back up a significant amount of data from an internal to an external hard drive on a consistent schedule, but our work computers are set to go to sleep if they haven't been used for 15 minutes. We are not authorized to change this. The back-up process takes longer than we are at work, so every time we leave at the end of the day, even if we leave the computer on, the back-up process is interrupted. When we turn the computer back on it shows the error message 0x80070037 "The specified network resource or device is no longer available."
How can we change the settings so that the data will continue to back up even if the computer goes to sleep? Or better, can we set it up in such a way that the computer will start the backup process when it starts to sleep once/week, so that it will do the whole thing overnight? My boss lost a lot of data recently and wants to be extra cautious proceeding forward. Any suggestions at all would be appreciated.

We are using Windows 7 and would like to do one full backup and three differential backups/month. 

Thank-you for your time!

[AnnMarie]

If you are not authorised to make changes, you will need to contact your IT Dept or the firm that is contracted to maintain your network.