My windows defender not run at startup?

[livx]

windows defender in my vista does not run at startup.i clearly sure it's not
running at startup when there is no windows defender alert when i try to open
fake "eicar.com" virus file (it's testing virus file which can be download at
http://www.eicar.org/anti_virus_test_file.htm

However windows defender can detect it after i manually open windows
defender.I already setup an option windows defender to always appear in
notification area but it's still failed to start at windows startup.

help me

 

[Dave M]

The way I check to see if Defender is running is to open Task Manager
(Ctrl+Alt+Del) and look for these two processes:
MSASCui.exe
MsMpEng.exe

I then look in System Services for the Windows Defender Service to be in
Started Status. If all three of these items are found, it's pretty certain
that Defender is operational.

Since you can detect EICAR when you manually start Defender, I think that
you're probably running Windows Live OneCare. Since OneCare is a superset
of Defender, the standalone Defender application is disabled when OneCare
is installed to avoid duplication. You'd be correct in that situation,
standalone Defender is not running. Since the Anti-Virus component of WLOC
can also detect EICAR, I imagine you may have temporarily disabled its
AV/AS component in order to test Defender. You wouldn't get any EICAR
detection at all in that case. I do think it's a good idea to test
Defender's real-time capability with EICAR, you just have to be aware of
how WLOC and other Anti-Virus applications interact with it.
http://windowsonecare.spaces.live.com/Blog/cns!C29701F38A601141!3842.entry

Let me know if the above guessing is incorrect...