Q:When I got my computer, I installed Windows 7 on it. There was only one administrator, me. Now, over a year’s time, I find that there are half a dozen different administrators on my computer. I didn’t change a thing; I don’t have that expertise or the courage.

Some are called System; some have my first name. The most obnoxious one is called “Trusted Installer.” I’ve found hundreds of unwanted little programs on my computer. Some are little snips of videos of boys riding BMX bikes (I have no children) and backgrounds called “Baby Boy.” There are audio and music files I didn’t ask for, didn’t download, and have no use for.

The infuriating thing is I can’t delete them. I get a pop-up saying I don’t have the right and only Trusted Installer has the administrative rights to say whether it gets deleted or not. I didn’t install Trusted Installer on my computer.

How do I expunge Trusted Installer or at least chain it in the dungeon so it doesn’t change things without my administrative permission?

— Michelle

A: Often, when a user installs an application, other things get installed, too. For example, when you install Windows, Trustedinstaller.exe is also installed as part of the Windows update process.

Such installers also determine the “owner” of files and directories. And I have indeed seen reports of users who install the Windows Media Player finding sample files owned by Trustedinstaller that can’t be deleted by the user.

If that’s the case, you’ll need to modify the permissions settings on the folder containing those files.

To do so, right click on the directory or file in Windows Explorer, then click on the Properties tab. Next, click on Security and then on the Advanced button at the bottom of the dialog box. In the Permissions window that opens, click on the Owner tab.

You will then see the current owner and you’ll be able to change it to your account. Click OK to save and exit.

This should allow you to delete the files and directories. The presence of a growing number of administrators, however, makes me wonder if you have also inadvertently acquired some malware that’s mucking things up.

Accordingly, I’d urge you to run a full scan with your anti-virus software and try running a good anti-malware program, such as MalwareByte’s Antimalware. You can download a free version at www.malwarebytes.org.

Q: I found have some files on my drive that are supposed to be photographs, but Windows won’t display them, even as thumbnails in Windows Explorer. They have the file extensions .NEF. Can you tell me how to open these files?

— Anne Jackson

A: .NEF is an extension used by Nikon for files in the cameras’ RAW format. RAW image files contain all the information captured by the camera’s sensor, plus metadata — including information about the camera that took the photo, such as the model and camera settings.

RAW images also contain any in-camera processing, such as white balance, as instruction sets rather than making changes to the underlying image data itself. As a result, you can make more refined adjustments to a RAW file than you can once you have exported it to TIFF or JPEG formats. If you want to view the .NEF file or convert it to another file format, you’ll want to download Nikon’s free ViewNX 2 program.

Questions for Patrick Marshall may be sent by email to pmarshall@seattletimes.com or pgmarshall@pgmarshall.net, or by mail at Q&A/Technology, The Seattle Times, P.O. Box 70, Seattle, WA 98111. More columns at www.seattletimes.com/