1- from distro homepage, trough distrowatch, or from here: on the right, in "main menu", there's "Download Linux". Download an iso image, then burn a bootable cd from it (not a regular data burn, note!)
2- the installation does format your harddisk, or at least part of it; modern installation programs can shrink existing windows partitions to make space for Linux, wipe out the whole harddrive and use an "automatic" partitioning or just let you do it yourself if you want to. you can also install stuff like ZipSlack on a dos/windows partition, but I recommend doing a "full" thing.
3- depends on what you do. office programs, email, browsing, image editing, cd/dvd burning, video and audio software etc. come right out of the box. more is on the net, easily available trough a package manager of some kind (depends on the distribution). if you want extra software and it's not available as a binary package already, then you can at least compile it yourself. software like Wine lets you run (some) Windows programs on Linux, or you can use vmware or other virtualization software to run a whole Windows OS on top of your Linux.
4- ask ZIFFDAVIS about that. you could contact me, but at the moment I'm unable to use any IM software so it might take some time and tries.