QuickTime, which comes from Apple, displays photos and videos, plays music, and performs various other multimedia tricks. Although the software is available as a stand-alone product, it comes bundled with iTunes–and that’s how it lands on most users’ systems. Install iTunes, and QuickTime (necessarily) sneaks in too.
Do you need it? If you’re an iPod, iPad, or iPhone owner, you need iTunes–and, ergo, QuickTime. The same is true if you like to watch movie trailers and other videos in your browser, as many embedded videos are encoded in a QuickTime-compatible format. My advice: Unless you have a specific reason for deleting it, leave QuickTime alone.
(For more solutions to perplexing PC problems, see “The 21 Greatest PC Mysteries–Solved!“)