Multimedia editing and analysis software
Zero-cost solutions recommended here: software included with your computer (providing basic functionality, sufficient for Music 666), or open source tools (which can be quite sophisticated).
Audio
Audacity, super open source and cross-platform (mac and win) audio editor. Get to know it.
Video
Windows: Movie Maker, included with Windows up to Vista; Live Movie Maker for Windows 7. Many professional packages are available; probably Adobe's Premiere Pro (see below) is most widely used.
Mac: iMovie is simple video editing software included with every mac; suitable for presentations. Professional package for mac is Final cut pro
You can download a 30 day trial version of the industry cross-platform standard, Adobe Premiere Pro
Image
Windows and Mac operating systems provide simple image editing software, e.g. iphoto for mac. More sophisticated is the open source cross-platform project, GIMP.