Get a Mac and you *really* won't regret it. iPhoto handles all 4000 or so of my pictures beautifully. Adobe designs their software for Macs so you know Photoshop/Elements will run well. The mini comes with Quicken and iLife and all sorts of good toys, plus you can use your current monitor!
You'll never have to deal with viruses, malware, and other bad stuff that slows down your machine. And there are plenty of Mac users around here who would love to help you out

Tutorials are the same, just remember that the screen shots will look a little different and you might have to hold down the Apple/Command key instead of the Control key sometimes... just a little trial and error and it won't be a problem. Since professional graphics people use Macs, you should be able to find plugins galore. And with the new mini, they're NOT overpriced! Remember, your time is money and every time you have to install camera software (iPhoto works with almost all consumer digital cameras) or reboot or check for viruses you're throwing time down the toilet you could have spent scrapping!