From looking on other forums this seems to be a fairly common bug at the moment with Windows Defender on Vista. This is what one user posted as a fix that worked for them:

 

I had the same problem, it has to do with automatic updates (even though it
says you are up to date, there are some missing). I turned off the windows
automatic update and unchecked options under recommended updates. (control
panel - windows update - change settings). Then I checked for updates - and
there were some. I installed them and then ran the windows defender update
and it worked. Don't forget to turn back on automatic updating when you are
done!

 

Hope this helps!

Thanks, i will try that and see what happens

Thanks very much, i did what you suggested and everything seems to be ok, with regards to the Defender problem, however the computer still freezes!

Glad you have managed to get the defender problem sorted, can you give a few more details about your system (graphics card, ram etc etc) as it might help people come up with some better suggestions for the freezing issues.

Hi There,

 

The computer is a Dimension 9200, 2048 MB of memory,graphics card is 256MB Nvidia GeForce and two hard drives of 160GB each, serial ATA (7200 rpm).

 

I hope this is of use to you.

It's possible that this is a driver issue as most manufacturers are still ironing out problems and even drivers that have been released don't fix all the problems. I would try checking directly on hardware manufacturers websites for newer drivers as they can take quite a while to filter through to the Dell site.

 

So for example the latest graphics card driver from NVIDIA for Windows Vista was released on the 20th February but the Dell site is only showing a driver from the 1st February for your PC. The link for the NVIDIA drivers is:

http://www.nvidia.com/object/winvista_x86_100.65.html

Hi There,

 

Thanks for that, i have downloaded the driver and i will see how it goes, once again, thanks for your help.

 

Steve.

Hi there,

 

After another phone converstaion with the dell technician, they have decided to change the computer, as loads of other people have experienced the same problems with vista, ie vista freezing and defender unable to check for updates.

 

Once again thank you all for your help and assistance you have given me.

 

Steve.

i'm still running into the problem with the error code.  i did what you said but my update says i'm up to date the defender says that say error code.  i looked online and people are saying the code means that my version is illegal but i got it from dell =\

MS posted a fix at http://support.microsoft.com/kb/934562/