No safe mode - but...
Here's a bit more detail:
The problem started (on 2 separate machines) from 2 different manufacturers after I ran SpyBot Search and Destroy to remove SpywareBot.SpywareStop from the machines. Startup gets as far as the login screen. I have just enough time to start typing the password and then the machine(s) shutdown.
Safemode runs to the point where I get a mouse cursur on the screen but then the machine(s) turn themselves off.
I have tried running Startup Repair but it reports, "Boot status indicates that the OS booted sucessfully."
I can get a Command Prompt from the System Recovery Options menu and have run chkdsk /r /f but to no avail.
I have tried restoring the machine to an earlier point but the problem persists, restore fails BTW (I have tried turning off all active protections, but to no avail).
I can log into Vista using the "Last known good configuration" from the Advanced Boot Options menu. Is there anyway to transfer the settings from the "Last known good configuration" to whatever set is being used for the standard startup?
<b>UPDATE: I just restored the virus using SpyBot and my machine will now boot. So, it would seem that the problem is related to how SpyBot is removing the virus/Malware.