Heh, sorry, I must reply.
Cost to have mine assembled for me: $45 bucks.
I know the difference between all those things, but I payed a small computer store to make mine for me because I didn't want to bother with it too much, again no problemo.
I have yet to need support, but for the record my computers came with a box full of manuals, and software which came with individual support numbers.
My computer came with Winblowz as well. And installing Windows is easy, it just takes time, more magic smoke. Most if not all premade PC's (factory or house made) come with windows installed on them, if you make your own computer and can do it, installing windows shouldn't pose too much of a problem.