Backup Application and Solution

Guys,

Scenario :

We have SQL Server 2008 Express and Management Studio in 40 Remote Places and  in each computer we have External HDD connected to it.

Solution Required :-

We need to backup the SQL Database on that HDD every day at 11.00 PM as a backup and each day it needs to overwrite the existing file.

What would be the best solution or application to do this everyday?

Please share your knowledge.

Thanks.