I can't seem to get automated backup tasks to run

I have purchased 3 copys for 3 customers Two on Vista and one on XP.

I can't seem to get automated backup tasks to run consistently.

My settings are pretty simple:

whole disk backup
run daily
incrementel
new full backup every 7 days

I am really frustrated, after hours of trying to get the tasks to run the end result was I was not able to charge a setup fee due to it not fully working.

Can someone pleaseee help me here.