Update Error 80244001

Hi I've been having problems trying to update Vista and Defender. I've gone through the process mentioned on this site to fix it:

Error 0x80244001 could be caused by a MSXML issue.

Register MSXML3.dll and see if it helps:

1. Click Start.

2. Choose Run.

3. In the Run box, type (or copy/paste from this post)

%windir%\system32\regsvr32.exe %windir%\system32\MSXML3.dll

(note the space there in the middle)

4. Click OK.

But when I do it comes up with another error ox80070005

I've bought Windows Registry Fix software in case that would help but it hasn't.

Please could someone advise me how to go about fixing this issue? Please note that I'm not very technically minded so plain English would be great

Thank you.