Defender - Automatic Update of Definitions

Hello,

Not sure if this forum or the update forum is the correct one. I have been
having issues with windows defender for quite a period of time now.

I am using Windows Vista 32bit, and for the first couple of months I had the
computer, defender would always update itself automatically, but then it
stopped working, saying it could not find any new definitions.

I assumed this was because there weren't any new ones out yet, but the
problem persisted for a long time and eventually I looked for help online.

The first thing I found which seemed to help was running the command prompt
and using winmgmt to scan and fix my repository, as it found things were not
in order. After running this it seemed to work and when I checked for new
definitions it found and installed them, and windows defender was running
again.

However since then it has never installed the new definitions automatically,
even though I have it set to do so, all of my automatic install and update
tabs are checked on. So I used to have to use the website
http://www.microsoft.com/security/portal/ADL.aspx to update the definitions
manually.

This seemed to work, and defender always told me the new version was running
after I installed the update, but I still wanted to try and fix the fact that
it wasn't working automatically.

Searching further I found a command posted on the vista64x forums to run
mpcmdrun and remove then update the signatures, but this doesn't update to
the newest. The newest version is 1.24.5706, but this command only updates
defender to the following:-

Service Version: 1.1.1505.0
Engine Version: 1.1.3109.0
AntiSpyware Base Signature Version: 1.24.4710.0
AntiSpyware Delta Signature Version: 1.24.5611.0

For some reason it will not update to the newest definition, and now when I
manually install it, although it says it is running the new definition, when
I use the mpcmdrun -RemoveDefinitions -All command, the information it shows
me says it was only using 1.24.5611.0 still in the delta signature.

I have no idea what I can further do to correct these issues other than
format my hard drive and hope that somehow it doesn't happen again. I believe
at some point when this first started happening I tried to force it to
install new definitions by clicking the red security icon when it couldn't
find any and searching again, then I got an error message which I searched
for but could never find any reference to - I never noted it down.

Can anybody help me with this issue? I believe when the problems first
started I may have had the definition shown in the base signature
1.24.4710.0, or a .46 extension around there. Is this the issue that my base
signature won't update? What can I do?

Thanks !