Vista SP2 Avast Servis Stop?

I would, but I don’t know how.
Are you certain there has never been another AV on this machine?

Hello,
try to uninstall Windows Defender. It causes some crashes quite often.

Windows Defender cannot be uninstalled from Windows Vista.
Can only be disabled, but i don’t recommend, I don’t think Defender is responsible for this.

Yeah. It’s not listed on add/remove programs applet.

I feel the same.