Thanks for your suggestion. I think I'll set up a DV in front of my computer to record down any paranormal activities. LOL

Are you sure virus is able to corrupt the BIOS?

My X51 recently got a magical problem.   After shutting it down, it will automatically startup randomly. Sometimes it start up during midnight, sometime in the morning. Sometimes it doesn't start up.     I search the internet, checked the BIOS option,  BIOS > Adavanced > power management setup > auto power > disable, and it is diasabled.   But it still magically start up automatically.      Now I must switch off the power after shutting it down.     Any idea what is happening??     My system is Win7.

I would check for poltergeist activity in your home first. A priest is good for fixing this issue if you find you have a ghost problem.

If you don't then I would check your BIOS. Find the Power Option. Then change the Wake On LAN or Wake On Whatever it says and disable it. Sorry, I don't know your BIOS 100% yet but there is an option like that in there. Find it and disable. Don't forget to sleep with the lights on for a while

If you did this, like you said you did over and over then try pulling the CMOS battery. It is a coin size battery on the motherboard. You will need to unplug the system to do this. Then open the case and pull that battery,wait a little and stick it back in. Then plug it back in and check the BIOS setting again. Make sure it is still off.

Another thing that can do this is a virus. Run some scans to make sure if the above doesn't work. There is also the chance of a bad BIOS doing this, upgrading it can fix it but I can not suggest that because upgrading your BIOS can brick the system if it is not done right. If you get to that stage try contacting Dell. That way if the BIOS update goes wrong they will replace your motherboard free of charge.

  Don't forget to keep the lights on for a few nights, just to be safe. This is very important, some ghosts can be really mean.  

Thanks for your suggestion. I think I'll set up a DV in front of my computer to record down any paranormal activities. LOL   Are you sure virus is able to corrupt the BIOS?

A virus can make it turn on. It is possible. This is a common issue but it's almost always in the BIOS setting. You need to double,triple check it's right. Then reset the BIOS and do it again. That is the most likely place for causing this.

If you are having "power on" issues I would recommend contacting support on the phone and request an internal power board swap.  the power board is separate from the motherboard inside the X51.  

As for poltergeists, hmmm I dunno.  don't upset them? :-)

Hello, new to the X51 forums here, as for the ghost restart issue (as my wife would put it) I just recently starting having the same issue last week. I thought it was me being sloppy, not the case. My X51 is used as a HTPC only. My house and network are like Fort Knox security wise, no virus issues and I've never tampered with the bios (all OEM settings). For the sake of argument I checked them anyway, all where they should be however, the random startup is real. If I shut down normally it starts itself in approx 2 minutes, if I do a shutdown via the power sw it restarts in approx 3 minutes. I had to unplug the dang thing. Weird. I noticed there's no conclusion to this thread so I'm assuming the problem is still out there?

If you don't see something in BIOS ... check settings in Power Profile (like "Allow wake Timers", etc.).

Are you sure another device is not sending a "Magic Packet" to wake? If also using HTPC as a "media server" or NAS-like for other clients, "magic packet waking" can actually be a desirable feature.

You shouldn't need to un-plug it (just Shut-Down). Even a wake-timer (scheduled task) or magic-packet can only wake from sleep (not from off).

I do shut it down normally and in about 2 minute it just boots back up, on it's own.

Thanks for getting back to me. I'll try disconnecting the network (Magic Packet) but as for the "Just Shut-Down" approach, I wish it were that easy. I do shut it down normally and in about 2 minute it just boots back up, on it's own. Odd!

Bios settings are good. I remove it from the network and the problem went away. I didn't find a virus in a scan (doesn't mean anything), maybe it's time to pull the hd drive and scan it from anothe system. Other than the virus option, are there any know mobo issues, I couldn't find any?

Scanning inside Windows should be fine. I like the free Microsoft Security Essentials on Windows -7.

If it's waking from OFF (truly shut-down) I'm pretty sure it's a BIOS setting ... at that point, the OS isn't running (nor could a virus or trojan be running.)

You mentioned your network "My house and network are like Fort Knox security wise" ... it there something special about your network or router?