XP Home Task Scheduler Error 0x80070005: Access is denied

I manually installed Backup on MS Windows XP Home as follows:
Double-click the Ntbackup.msi file in the following location on the Windows
XP Home Edition CD-ROM to start a wizard that installs Backup:
CD-ROM Drive:\VALUEADD\MSFT\NTBACKUP

On attempting to schedule an automatic weekly backup I get the following
Task Scheduler error screen:
“An error has occurred while attempting to set task account information. The
specific error is: 0x80070005: Access is denied. You do not have permission
to perform the requested operation.�

My Account Type is Administrator. Please can someone assist me. I do realise
this is a software question, but I am not getting a reply from the other
categories.

Many thanks
Margy Sneeden
Durban, South Africa