TideLog Posts Tagged “Windows”

I’ve had this problem a few times on my laptop. It occurs mostly when the power suddenly goes off and it switches to battery. You lose all capacity monitoring, and can’t tell how much is left. The system tray icon changes to this:

no battery detected

Microsoft’s forums are hilarious. Their “Most Valuable Professionals” give the funniest canned cut ‘n’ paste responses, from, “Your power driver is corrupt” to your “Windows needs reinstalling!”. I know exactly what causes it, and it ain’t anything to do with “power drivers” or corrupt Windows. It’s the little monitoring chip in the battery. Like a lot of integrated electronics, it sometimes gets confused. Sudden switchovers from mains to battery tend to cause it, especially if there’s any surges from the battery as it kicks in.

The age old advice of “Reboot!” is the wise advice. If that doesn’t cure it, turn your machine off, remove the mains and battery, and hold your power button down to discharge the circuitry in your device (apart from the RTC circuit, but this doesn’t matter), that should cure it. Removing the battery opens the circuit to the sensing system in the battery, and resets it.

Simples. I hate MVP’s, they go on a 5 day course and think that gives them a Professional title? I’ve done MVP courses, but have the skills and years of software and electrical experience to further and back them up

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Something we frequently do at work is a full backup and reinstall, my nickname for it is a Wash ‘n’ Wipe. It goes like this: Image the boot drive to one of our backup server drives, wipe their drive and reinstall Windows, find drivers and programs, then plug the backup drive in and copy their stuff back.

To cut a very boring long story short, Windows decided to letter the backup drive C:, called the boot drive F:, and once our drive was removed, it hung at the “Welcome” screen. It’s just so silly I can’t think of a decent analogy.

Fortunately, I had an idea how to fix it, and it worked. It works on Win XP/Vista/7. Reproduced here mainly for my own reference, and my techies, and so you can remember reading about a fix if it ever happens to you:

  • Run regedit (Windows key + R, “regedit”, enter, or, click Start, Run, type “regedit” without quotes On Windows 7, the Run command is under All Programs/Accessories)
  • Go to HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
  • Delete ALL of the keys listed, for example \DosDevices\C: to Z:
  • Pray, whilst rebooting, and pray some more as you come to the welcome screen

It worked for me, and that computer’s back with a customer hard at work. I’ve found this works on XP/Vista and Windows 7. I have a testbed with all 3 installed for this kind of testing.The more problems you can solve, the more custom you get, and don’t have to turn away! Here’s a screenshot under Windows 7 I did:

All the drives with ???? are removable USB drives maps (on my system!). They’re perfectly safe to delete! Yours will likely be different.

This particular registry key – HKEY_LOCAL_MACHINE/SYSTEM/MountedDevices – lists the mapping between the disk drives on your computer and their respective drive letters as visible in My Computer. Windows sometimes gets confused about how to refer to your boot volume (should be C:/), and if your boot volume’s drive letter changes after you install XP, it will likely get stuck starting up and hang just before the Welcome/login screen.

If your machine WON’T start, obviously you can’t just run regedit, but there are ways around it. There do exist commandline tools you could run from a floppy disk, but by far the easiest way is to grab a liveCD that contains a registry editor. I use Mini XP on Hiren’s BootCD, but this tool should do the trick easily enough for most.

Caution: If you have programs installed to drive letters other than C:\, be aware this could cause issues with them. Windows may be intelligent enough to reassign the driver letters with respect to installed programs, then again, being Windows, it may not be. I haven’t tested this analogy yet, but will try to, and report back.

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