Running Vista Home Premium.
He complained of failing to boot in either SAFE or Normal mode.
Black Screen only with mouse cursor arrow moveable but no functions, no icons, no task bar, ... just stuck.
I ran the Quick StartUp Repair using the Vista DVD (and followed BleepingComputer's tutorial for Vista Repair) but to no avail.
Or so I thought.
No benefit occurred from the Quick StartUp Repair.
I was able to access System Restore, but each of several Restore Points failed with 0x800015 or 0x8000B7 errors.
So I ran MS Windows Memory Test -- No errors detected....
But lo and behold, the darn machine booted Normally and is fully functional now.
It simply automatically booted after Memory Test.
I've been able to restart 3 or 4 times
... No idea why it's working now, and not before!
There is one item in MSCONFIG - StartUps that is written in Chinese Language Characters... Unknown.
(But this is an Acer - manufactured in China... so it easily could be legit.
I've installed and run ATF-Cleaner, AVG AntVirus, AVG AntiSpyware.... Nothing bad showing.
AVG AntiSpyware removed a ton of Cookies... That's all.
So the darn machine is now running fine now, and I feel lucky.
Trouble is... I don't like "feeling lucky" when it comes to Vista problems mysteriously resolving themselves.
There are no warnings in Device Manager.
There "was" an IE Cache overflow.... 74mb on a 50mb limit
The hard drive needs defragging.
Nothing else prominent that I can see.
Your ideas will be appreciated.