Showing posts with label tools. Show all posts
Showing posts with label tools. Show all posts

Monday, November 22, 2010

Windows 7 Wireless - Poke the exclamation point

I spent a good two hours today learning how to make Windows 7 wireless network connectivity behave more like I expected.

The problem:
Windows shows a yellow exclamation when my internet connection is interrupted, but it remains there even after I'm sure my connection should be back up.  A Windows XP computer and and an iPhone both survive the interruption, but my Windows 7 notebook is confused and keeps my web browser from connecting.  It is a serious interruption in my day to restart my machine completely.  The goal was to force my network connection status to be up-to-date, so I can continue working without restarting.

The background:
I have an internet connection that is a little flaky and will fail for 2 min about 3x week.  The root cause is probably the service provider or my Linksys router, haven't sorted out which it is yet.  

Solved:
The culprit seems to be the "DHCP Client" service not being correctly controlled by the "Network Store Interface Service".   Restart "DHCP Client", and Windows 7 will be forced to figure out the actual status of my network connection, including the yellow exclamation point in my systray.

Instructions:
1. Go to Start->Run, then type "services.msc" (remove the quotes) in the run box.  
2. In the list that appears, right click on "DHCP Client".  
3. Click restart.  
4. Click on "Yes" on the warning box that appears.
  
Wait 30 seconds, and you should see the yellow exclamation icon disappear in your tray.  If your internet connection is truly working, your Windows 7 machine should now be able to search the internet.

Solved in detail:
I found that Windows 7 contains the list of services, below, that all seem to be directly related to my wireless connection. I know a few of these from Windows XP, but several are new, and have confusingly overlapping descriptive names.  I could make educated guesses to which did what by reading the service descriptions, but it took 2 hours of trial and error to find which services actually affected my connectivity.  More importantly, windows seemed to block on the yellow exclamation icon (bang symbol) until the connectivity returned.

Windows Services related to this issue:
1. Network Store Interface Service -- This seems to be the actual controller for all network connection activities.  Many services depend on it, including DHCP client.  Wrinkle 1: When I restart this service, it will stop the DHCP service.  But, when the starts are fired, it will not start the DHCP service.  This causes the internet to stop working on my computer.  See (9) below for more.  Wrinkle 2: When restarting this service, (6) below falls into a defunct state, which throws the error "Error 1051: A stop control has been sent to a service that other running services are dependent on.".  This makes a mess of my Windows 7 connection state.  See (6) below for more information.
2. HomeGroup Provider - depends on (1) above, but doesn't interrupt internet connectivity.  Restarts with (1).
3. Network List Service - depends on (1), but doesn't interrupt internet connectivity. Restarts with (1).
4. Network Location Awareness - depends on (1), but doesn't interrupt internet connectivity. Restarts with (1).
5. Network Connections - depends on (1), but doesn't interrupt internet connectivity.  Restarts with (1).
6. Computer Browser - depends on (1), but doesn't interrupt internet connectivity.  When restarting, this service will fail to stop with a Error 1061: "The service cannot accept control messages at this time." message.  I found that if I used the Sysinternals Process Explorer tool as an elevated user, then found the process that contains this service, then killed the containing process, I could then restart any of the services 1-9 above without issue.
7. Workstation - depends on (1), but doesn't interrupt internet connectivity.
8. IP Helper - depends on (1), but doesn't interrupt internet connectivity.
9. DNS Client - depends on (1), but doesn't interrupt internet connectivity.
10. DHCP Client  -- This was the issue.  When not started, a bang (exclamation) shows on my network bars icon; when started, bang immediately dissappears, and my internet connection works perfectly.  Stops with (1), but does not restart with (1), even though (1) appears to start successfully.

PS:
As background, I based all my troubleshooting on an Acer Aspire One, 1GB RAM, with Windows 7 Starter Edition.  I expect that the problems above are Windows 7 specific, though, and not necessarily related to the Acer or Starter Edition brands.




Monday, October 18, 2010

Save time in complex spreadsheets - Evaluate Formula

You've probably been there.  You have a spreadsheet formula that is complex, and it is not giving you the answer you expect.  You have looked at this spreadsheet for longer than you want to, and you don't know where to look next to find the problem.

1. First, congratulations.  You realized it was the wrong number before you sent the results out to the rest of your team.
2. Second, you still have a problem.  You can't find the error in the middle of all the parentheses, functions, and other clutter.

In comes "Evaluate Formula" to help solve the problem.  Evaluate Formula is used to "step through" the portions of your formula.  "Step through" is a common programming term that means to do something one step at a time, so you can find the problem in the middle of a multi-step process.  

Usage:
Each time you push Evaluate, one single portion of the Excel formula in your current cell is executed.  
Press Evaluate, then look to see if that portion of the formula pulled in the numbers in Excel that you expected.  Excel highlights in blue in the upper box which portion of the formula it just ran, then shows the result in the lower box.  If that intermediate result was correct, press evaluate again to see the next portion.

Repeat until you find the number Excel is using that you didn't expect.  Correct that portion of the formula, and then Evaluate again to make sure that new cell formula gives the correct result.  This process can take time, but it also gives you a step-by-step task list of items to check.

How to find it:
Evaluate Formula is found under Tools->Formula Auditing in Excel 2003.  Search for "Evaluate Formula" in Excel help to find it in newer versions of Excel.



More information:
Additional helpful details can be found found at Mr Excel (a straightforward, reliable source of help) and on Microsoft's website.