Vista - Windows Defender is out of date problems

I have vista premium home 64 bit.
My windows defender keeps telling me its out of date. I tried to fix the problem via the microsoft site and it took 40 minutes to download the update definitions and whatever. I am still getting that message windows defender is out of date and no new definitions.

I took off my anti virus program, Webroot AntiVirus and with antispyware thinking this crummy program corrupted my Windows defender. So I currently do not have any virus protection program on my computer.

I have noticed there are many problems with webroot antivirus on the internet, as well as experiencing my own problems with it and their terrible "support".

I have not been able to successfully update their newest update and was getting a message that webroot was on but not unable to communicate with Windows Defender.

So, is this awful program, webroot responsible for corruping my Windows defender?

If not, how do I restore Windows defender?

I am a computer dummie, so easy is better for me.

Your best and simplest bet is to get FREE Microsoft Security Essentials. It is made by Microsoft and will disable Defender since it will no longer be needed. This all in one program is all you need.

Computerdummie,
Firstly you are not a computer dummie. A dummy is one who doesn't ask questions.
How did you remove Webroot AntiVirus?
If you decide to follow the advice given by rhlhamlet refer to the link below.
Read carefully the About, Resources & Support Tabs. I suggest you also look at the Installation video.
Let us know what you decide.

Virus, Spyware & Malware Protection | Microsoft Security Essentials

Yes, I removed Webroot.
I downloaded Microsoft Security Essentials and still have many problems.
I get an error message that microsoft security essentials and windows defender saying they are out of date. During this very frustrating process of trying to download updates, I have discovered I have NUMEROUS FAILED WINDOWS UPDATES, dating to Sept 4. I have no idea what to do with this huge mess. I suspect my previous failed windows updates have something to do with my initial problem of Windows Defender not able to update. How do I start over and update all windows updates and get rid of the failed ones?! This frustration is not good for my heart palpatations.