Quicktime is certainly not "malware," whatever you think of it. It doesn't slow down your computer, as the only part that'll run in the background is the little taskbar menu. You can in fact turn that off, either through Quicktime's options, or through the Services applet or even msconfig. Dark is right, you just have to go through the options and trim it down to size.
I rather like Quicktime. Better quality than WMP, and I've never had any problems with it. 'Course, I do hate the whole paying for "Pro" functionality, but there are "ways" around that...