1) There's no such thing as Windows 8 (yet). You can dual-boot Windows XP, Windows Vista, or Windows 7 by using the built-in Boot Camp software- this gives Windows full access to all the power in the computer, but you have to restart the computer to switch between Windows and Mac OS X. You can also virtualize, using VMWare Fusion, Parallels Desktop, or Oracle VMWare which lets you run Windows on top of OS X, but it comes at a performance penalty. Don't use virtualization to play games because it doesnt work very well.
2) Of course. The default music library on OS X is iTunes. It doesn't come with the codecs for Windows Media Audio files (WMA), but you can download them- just like you need to download the codecs for Apple Quicktime files (MOV, MP4, M4A) on Windows.
3) Mozilla Firefox is. Microsoft stopped making Internet Explorer for non-Windows platforms around the time Windows XP came out.
4) Apple's TextEdit replaces both Notepad and Wordpad. There is also a built in calculator. For the productivity suite, you can either use Microsoft Office for Mac, Apple iWork, or Oracle OpenOffice- they all can open and save Microsoft Office files (.doc, .ppt, .xls).
5) Again yes. Apple follows a pretty standard format for non-Windows platforms, which Microsoft is more closely following with Windows Vista and Windows 7. You have your personal folder, which is located in /Users/ (Unix-based systems, like Mac OS X, don't have drive letters). In that folder, you have Downloads, Pictures, Music, Movies, Documents, Public (shared documents), Sites (in case you want to host your own website- OS X comes with the tools for that), Library (to store user-specific application files), and Applications (to store applications that are only installed for one user)