Fail to install .Net 1.1 SP1

Dear All,

My laptop is a Toshiba Tecra w/ Pentium M at GHz with 1GB RAM
Hard drive 60GB - Free 30GB
I have Windows XP Professional SP2
Antivirus/antispyware, etc: Norton 360 Suite
I run automatic update daily.
Today I got the following update: Microsoft .NET Framework 1.1 Service Pack
1. I have run it 20 times at least. The session initializes normally but it
always fails to complete. I only get this mssg: "Some updates could not be
installed" + "The following updates were not installed: Microsoft .NET
Framework 1.1 Service Pack 1." The yellow shield in my tray keeps reapearing
over and over again. I tried rebooting it but the problem still persists.
My current .NET 1.1 version is 1.1.4322.573 which is the original RTM.
Pls HELP !!!
Thank you folks ! As always your help is greatly appreciated !!!