Windows XP Registry

I am a Windows XP Professional user and need assistance to correct the following system errors.

From our original Service Request, a duel boot option was inserted in the boot stream. It offers an option for booting to either Windows XP or simplyWindows. I’d like to remove this option.

My system is schedule to run back-up each week, but this software has never run at the scheduled time. Please show me how to set-up and execute
scheduled programs.

IMPORTANT! Registry contains invalid file associations and I can not get full access to
the registry. How may the registry be repaired?

Often during execution, the PC will freeze and run out-of-memory. How can this be prevented.

PC here is a PIII,
1000 MH,
“C” Drive is a 40GB
“D” Drive is a 30 GB
RAM is 224 Meg.