Starter gear

1.
Yes that is a good controller choice. If the pads are worth it is a good question. I myself do not think so as the older Mixtrack pro worked really well too. However there are some features that the pro2 has due to the pads (like insta loops).
Is this necessary for a beginner? No not really you should focus on the basics anyways. So in the end, your decision.

2.
HP, well I work at a company which sells them, but I can only say they hold up OK and warranty service is OK. Other than that I am a Mac guy and have exclusively used Macs for Music since 1999…

3.
Virtual DJ is good, but honestly you would need the Pro Version. And the pro version is rather expensive as a first investment. Of course it is justified by the simple fact that it comes with lifetime updates, so in the end not that problematic.
However the Mixtrack Pro does also support Serato DJ Intro (free) which is OK if you do 2 decks and will almost certainly get you through the first weeks of learning as the integration is really tight and well and you can Upgrade to full Serato DJ afterwards which has a similar tight integration.

4.
iTunes is fine. For 90% of my song purchases I use iTunes and it is perfectly fine. Yes there is some odd remix or other version of a song I want that is not available on iTunes and then I get it on another service. But honestly most songs are cheaper on iTunes and the encoding (iTunes Plus which is standard now) is totally fine to DJ with.

1. Numark Mixtrack PRO, from my own experiences its a OK beginner controller, the lack of VU meters did not bother me much, but the one thing is bugged me is, no gain knob on it, in the club in-house mixer i have to turn the gain all the way up so it at least can go hand to hand with the CDJ quality sounds, even tough the gain already at maxed, it still not satisfying to my ears compared to the in-house CDJ quality, the Numark Mixtrack PRO 2, might offer a better sound card for it, not sure as I never tried them

2. Windows base laptop is a hit and miss most of the time, depends on how well you can self maintenance it, my bedroom is always messy, i burp in public, this why I much prefer Mac it can take care on its own

3. Virtual DJ, choosing program is much more a personal taste, the home version of Virtual DJ only allowed you to mix with controller for like 10 or 15 mins i believed, more than that you have to buy the full version. As terry already mentioned Numark mixtrack came with Serato DJ Intro, it should be fine for your normal mixing, the only difference i see between Intro and full version of Serato is the recording function

4. Itunes, is OK too, not only for purchasing, you can use Itunes to arrange your playlist nicely, most DJ use this to arrange / re arrange their playlist, plus the music you see in Beatport, you can purchase it much cheaper in Itunes, the other option is a DJ Music Poll where you pay monthly designed exclusively only for DJ (well its their policy anyway)

Rumur, I am a NOOB, I have a Mixtrack Pro 2, it has been a great learning tool, but I am now upgrading to a new controller. I got the MTP2 in June 2013. I have in no way outgrown the functions/features of the hardware, or the software really. I am looking forward to the full Serato DJ, but Intro is nice too. I would say this, even on decent headphones(not $100+ cans, but decent ones) the MTP2 is not nearly loud enough for playing loudly and still hearing the cue. I mirror the above statement, that the master out isn’t nearly as loud as many other devices, like CDJs and even my laptop headphones split into RCA then into the mixer, or my iPod…. both register a louder input on the VU meters on my Stanton mixer. If I were you, and looking in the price range of the MTP2, I would seriously consider the Denon MC2000 (what I’d get if I had it to do over), or the Pioneer DDJ-SB (what I’d consider as an option to the MC2000).
As far as the other topics, I personally can’t add much to what was said already, I use a Gateway that we got a year ago, it has 4BG of ram, Intel B960, and was CHEAP! It runs Serato Intro fine, I have played with Maschine 2.0 on it, and it seems to run it OK too… I will soon be buying a dedicated “music” computer, and may just get another of these as they are still at Wally World for $328. I know I could use a better computer, but I think one without viruses, games, tons of pictures and such, would do even just a little better than this one. In a year or two it will become the backup, the one I’m typing on now, will be solely for family use, and the new one will be my primary ‘music’ computer. Backup your music and library info…. I hope to get another HDD soon just for a backup, backup…LOL For music, I still get most of my tunes from the record shops, either on vinyl or CD. I do get some from emusic, and Beatport, but have yet to get iTunes set up…. SOON, soon I plan to do that, as I have been asked to do a gig of Country Western, and I don’t have enough country in my collection to do a whole evening of just country. Hope my rambling helped, keep us posted and let us know what other stuff you’re pondering……….Keep Shining……….. Moonshadow