Mashoreen asked the Answer Line forum why taskhost.exe--usually a small background application--was consuming 50-percent of his CPU.
Like the title character from Woody Allen's Zelig--who changes his political beliefs, ethnicity, and even his race to match those of the people around him--Taskhost.exe can become pretty much what any dynamic link library (.dll) file wants it to be. Libraries can only run through an .exe program file, and taskhost provides that service. This is why you'll often see multiple instances of taskhost running at the same time.
But this also means that if Taskhost appears to be hogging resources, some other file is really to blame. The hard part is tracking down and identifying just what .dll is the culprit.
To see what taskhost (and other processes) are doing, right-click the taskbar and select Task Manager or Start Task Manager. Click the Processes tab. Click the Image Name column header to alphabetize the processes so you can easily find all of your currently-running taskhost.exe processes.
If you see a taskhost process with a large CPU number, scan for malware. Remember that if your PC really is infected, your regular antivirus program is quite likely compromised. So get a second opinion from one or more on-demand malware scanners. See Will One Antivirus Program Take Care of Your Security Needs? and Remove Hard-to-Kill Malware for more on that issue.
If malware doesn't turn up, download and run Windows Sysinternals Process Explorer (you don't have to install it). Once loaded, you can find and point to the hoggish instance of taskhost.exe. To see what .dlls are using it, select View, then Show Lower Pane. Press CTRL-d to make sure you're viewing .dlls and not handles.
Read the original forum discussion.
Contributing Editor Lincoln Spector writes about technology and cinema. Email your tech questions to him at firstname.lastname@example.org, or post them to a community of helpful folks on the PCW Answer Line forum. Follow Lincoln on Twitter, or subscribe to the Answer Line newsletter, e-mailed weekly.