Why does my PC restart after logon or at the welcome screen?

Question

I have the issue of the Vista rebooting everytime I get into Welcome login screen. I see a continous disk activity and then after a moment reboots. I can login within that time. However, I cannot do much and can launch task manager at the most. I can see all the process being killed and it automatically logs me off after a moment(around 20 secs) and system reboots.

I loaded this machines registry winlogon hive on a different machine and I see the date value of userinit is not altered and is userinit.exe.

Any other clues

Answer 1

It could possibly be malware or similar - I remember about a year ago dealing with a machine where someone put a link to shutdown in the startup group.

As you seem to have the time to launch task manager, I recommend that as soon as you boot in to Windows, you try to type the following in to the run box:

shutdown -a

This should abort any in-progress shut down.

It will only work if a shutdown is in progress so if it doesn't go straight away, try launching it a few times.

Once you are in, try and do some digging around to see what is causing it.

I would recommend using Microsoft / Sysinternals Autoruns and also looking in the event viewer for clues as to what is going on.

Please give feedback on if this works, or how far you get and I (or someone else) will try to help further.