On Windows, you may come across a background process called "iTunesHelper.exe"; this is not a virus or spyware. It is a process related to iTunes, and it monitors plug-and-play operations of iPods, iPhones, etc. iTunesHelper.exe is the application that launches iTunes whenever you plug in your iPod or iPhone to your computer.
If your computer critically lacks memory (RAM), you can kill the iTunesHelper.exe process; keep in mind that iTunes will not launch automatically whenever you try to sync your iPod or iPhone. If your computer isn't crawling to a halt for lack of RAM, let iTunesHelper.exe run in the background.
You may also run across other iTunes services called iPodService.exe or ApplMobileDeviceService.exe, on Windows - these are more recent additions to the iTunes ecosystem, and, like iTunesHelper.exe, should preferably not be disabled unless you are critically running low on computer memory. The iPodService.exe process is self-explanatory, and disabling it in recent versions of iTunes will prevent iTunes from detecting iPods you may connect to your PC (or Mac, as the case may be).
Disable iTunesHelper in Mac OS X
The iTunesHelper process also runs on Apple computers. On Mac OS X, the process is listed under System Preferences > Accounts > Login Items, along with other startup services. Here again, you should not disable iTunesHelper from starting with you Mac - it consumes very little system resources, and disabling it could cause seemingly unrelated, thus hard-to-troubleshoot issues.
Disable iTunesHelper.exe in Windows (XP/Vista/7)
To disable iTunesHelper.exe and prevent it from starting up with Windows, uncheck it under the MSConfig startup tab (Start > Run > Type MSConfig > Hit Enter). Note that iTunes will sooner or later automatically re-enable the process. For this reason, and given that iTunesHelper.exe is a legitimate Apple background process which typically consumes less than 5Mb of RAM, letting the process run might be simpler!