Definitely Vista, I had a computer built for me at a shop ages ago, (wish I had done it myself to be fair, more fun) he asked me which operating system I wanted, I said Vista, to which he replied: you sure? how I wish I had listened to him, nothing worked properly, was always crashing, I was even struggling to find antivirus programs compatible, it was once responsible for destroying one of my keyboards as I was that frustrated with it, I just reverted to xp which was loads better.