Run As window

What causes a "Run As" window to appear? when I try to logon to certain search engines,
I get the message Run As then the question, "Which user account do you want to use to run this program?"
why do I get this question?

 

http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx

I would run this and when you come to this popup check with process explorer to see which process is running that would ask for this, you can right click and choose search online for any process that you are not familiar with.

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how many users are on the pc??

You can disable the Run as service AKA "Secondary logon service" -

Right-click My Computer/Manage/Computer Management,expand the Services and Applications/Services.

In the details pane, right-click the Secondary Logon service, and then click Properties.

In the Properties dialog box, set Startup type to disabled, and then click Stop.

After the computer stops the service, click OK to close the Properties dialog box,
and then close Computer Management.

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run scans to check for malware and what is your current antivirus??

Download, install, update and do full scan with these free malware detection programs:

Malwarebytes Free (MBAM): http://www.malwarebytes.org/products/

SUPERAntiSpyware: (SAS): http://www.superantispyware.com/

Remove all found, reboot, and run again until scans run clean, these can be removed afterwards if you so choose. Run scans one at a time, please.
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http://www.pcreview.co.uk/forums/screen-called-run-keeps-popping-up-t134013.html

http://forums.techguy.org/windows-xp/913627-xp-registry-problem-annoying-run.html

further reading

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