I own both Mac's and PC's and I've had to use both for work and home use so I'm going to suggest going Mac to you specifically because you've emphasized "newbie" and ADD.

If you have a technological interest, like to "tinker" with hardware and actually enjoy poking around the net for hours trying to get 3rd party hardware drivers and in general, spending significant amounts of time and energy constantly updating software...go PC.

That being said. If you were to learn computers from scratch on a PC you would, out of shear necessity, possibly become proficient at the Windows operating system. Then again, you may just become so frustrated that you start to questioning how much quality really costs. By that I mean, do you want to save money by getting a cheap PC with a questionably stable OS, or would you rather pay more upfront and get a more user friendly OS?

As far as reliability is concerned, my first iMac was a G3 with 512m ram and a 6 gig hard drive. No problems until last year when the power supply went bad. We're talking about almost 9 years of continuous use. PC's? I lost count of the power supplies, bad motherboards, inexplicable crashes leading to lengthy system reinstalls...and that's just on my own PC's, not the ones at work.

Go Mac. You'll only cry once.