warrendr

I am getting two problems with Windows Defender...

Firstly it is not letting me start the service. When I try and turn on the
System I get and error as follows:

'Security Centre can't turn on Windows Defender. Please try again later'

I also get:
'Application failed to initialize 0x800106ba. A problem caused this
program's service to stop. To start the service, restatrt your computer or
search help and support for how to start a service manually.'

I have tried re-starting, starting manually etc and tried a number of things
suggested on the internet. But is still is not resolved.


Secondly, Windows update will not update Definition Update for Windows
Defender - KB915597 (Definition 1.19.2720.2). I am getting the following
error:

Failed: 1 Update
Code 8007003

Can anyone please help.
Thank-you.

OS: Windows Vista Ultimate.