How complitely turn off computer?

Question

How complitely turn off computer?

Answer 1

Are you talking about where it shuts itself down after going through the shutdown routine?  If it's not doing it automatically when you issue a "shutdown -r now" (or the like) then it's probably an issue with power management.  There's a few ways to tackle that.  Either use APM or ACPI.  ACPI tends not to work all that great on computers that have really old bios.  In that case it's better to utilize APM.  Probably your issue is that the your system may not support ACPI very well or even at all.  However, it may support it, but the kernel is turning it off by default from detecting your BIOS being dated beyond a certain point in time.  They did that to error on the side of caution.  They opted to choose a conservative default assumption since it makes more sense in that at least most systems will be able to boot up without any problems by default.
My computer used to be able to shutdown automatically through the use of APM, but not ACPI (ran into this issue when I upgraded my kernel from 2.4 series to 2.6 series back when I ran with Debian), but I ended updating it's BIOS and it worked fine with ACPI from there on.  My system is pretty old too, so it doesn't completely implement ACPI.  I think it's laptops that tend to make fuller use of ACPI anyway.  However, it seems like most desktops with the last 8 or so years make some minimal use of it at least.  So you can see there is many ways to approach this issue. 
First thing to try is to look around in your BIOS setup to see if there is any ACPI related setting, like mentioned earlier.  That's a good place to start.  If you don't see any settings, it either means that your BIOS setup either don't allow you to set ACPI, doesn't support it, or just the current version of your BIOS doesn't allow changing related settings or make use of it.  So naturally, the next thing to check is the manufacturer's sight for your motherboard and find any BIOS related info.
Upgrading the BIOS is probably the most elegent solution but it can be openning up a whole can worms if you don't know what you're doing.  If you botch flashing the BIOS you run the risk of turning your motherboard into a paper weight.  So the key there is make sure you at least read your manufacturer's instructions carefully and also make sure that your use the right utils and BIOS version for your BIOS and motherboard.  And don't dare have a power failure or shut the system off while it's rewriting the boot block.  That where people run into a serious problem of rendering their system completely unbootable since the system no longer has the most basic of code needed to even get the system to a state that it can even begin bootstrapping.  Technically, the motherboard isn't probably trashed, but at that point you have a chicken before the egg syndrome going on.  You can't get it to boot far enough to boot to anything, much less a floppy, to be able to reflash the bios to get yourself out of the pickle.  So when, and if that sort of thing happens, then it would require replacing the BIOS chip itself which may or may not require soldering. 
Anyway, don't let that scare you, it's just to point out that when you're doing things like flashing a system's BIOS it's critical  to do it right since it's modifying the system on such a fundimental low-level.  If that part of the system isn't functional, everything else, like HD and floppy being able to load anything, is a moot point.
If all of that stuff makes you uncomfortable, you may opt to utilize APM instead.  I can't remember exactly how to instruct the kernel to use APM instead of ACPI.  I believe there is kernel parameter you can set in your bootloader's settings.  I can't remember it off hand.  Sorry.