Hello dbhsfellas,
I've heard that the Microsoft Vista upgrade takes some major hardware requirements that maybe your HP won't have. You'll need to look into the minimum requirements.
OK here's my list of things I like about the Macintosh over Windows. I'm sorry that it is so long, but that's how it goes.
* No computer viruses.
You hear from the Windows people that it's because there are fewer Macs out there, but I think it's because of the Mac OS and it's Unix kernel. That doesn't explain why Vista got viruses before it was officially released. The Macintosh comes out of the box as a closed system. If you want it to be networked and remotely operated, you can make that happen, but you have to change it's settings first. Windows machines come out of the box as an open system. That's so the IT guy can set up the hardware, attach it to the company's network, and install the software remotely from the comfort of his own desk.
If you want to install any kind of software onto your Mac, you first need to type in your administrative password. There is no auto-install for a virus to attach itself to your Mac without your Okay. That is the simple answer why there hasn't been any viruses for the Macintosh in the past 6 years. Another is that first year programmers learn how to create simple Windows script viruses their first year of class. Mac programmers simply love their computers and have no desire to create such an abomination. We love our Mac programmers and happily pay what ever they ask for their good, hard work.
* Games.
I enjoy the games that I play on my Mac, but It's true that there simply aren't as many games out there for the Mac as Windows. Hopefully, with the Mac now using an Intel processor, we will start to see more games being developed for the Mac. But, honestly, don't most people simply get their gaming fix by playing with video game consoles (such as NES, PS, Wii, or XBox) anyway, rather than playing games on their computers?
* Software.
There is a lot more software for the Macintosh now, than before Mac OS X arrived. Much of the Mac's new software is simply Unix ports. There is also a large open source and public domain/shareware development community that has been supporting the Mac OS.
http://www.apple.com/downloads/macosx/
You can actually run Unix X-windows on your Macintosh now too. Apple has been designated as the largest distributor of Unix in the world. If you have one of the new Intel-based Macs you can now run Windows programs natively using a program called BootCamp. There is also a Java Virtual Machine for the Mac too.
There's still a ton of programs made specifically for the Mac. Most of these are programmed in C or machine language, so they're lightening fast. Apple watches over their developers closely, to make sure everything runs like it's supposed to; that it runs the Macintosh way. There's also a lot of Windows ports too. I use Microsoft Office on my Mac at work all the time. Although the Macintosh versions of Windows software are way behind in features than their Windows brethren, the Macintosh programs seem to run better, faster and are not as susceptible to problems as the Windows ports. Go figure!
Where the Macintosh really shines is in the creative software area. I'm a printer, so I know that the Macintosh pioneered desktop publishing. I think that most structured drawing, paint/graphics, and music programs got their start here too. Video and film editing and production is now very big on the Mac. Many people complain about how expensive some of these programs are, but frankly, professional programs are always more expensive than the cheaper consumer-level programs that are out there. Stuff like iTunes, iPhoto, iMovie, iDVD, etc. come free with your Macintosh, while other programs are quite affordable.
http://www.versiontracker.com/macosx
* Less problems
The Macintosh simply works. There really isn't very many problems using a Mac compared to a Windows PC. Check out the computer questions here on Yahoo! Answers. There are a lot of Windows, "Why can't I get this to work?" questions here. Even though there are a lot of Mac users here, there doesn't seem to be very many Mac questions. Right, it's because the Macintosh is a little more proprietary and you really need to buy hardware that tells you that it's Mac compatible. You can't just buy some cheap hardware, piece it together, and make a Mac, like you can with some PCs. But, then, you don't have Plug-and-Pray either. The Mac simply works.
* Mac OS X
It's a very simple, basic, easy-to-use OS. It's highly graphic, so your kids or your grandmother could learn to use it, and it's also got a terminal, so the geekiest guy can enjoy using it to it's fullest extent. Windows users will recognize many of the same features that they use on their OS, but there are a few things that are strictly Macintosh.
http://www.apple.com/support/switch101/
http://www.apple.com/support/mac101/
I have loved it because it's always responsive. You throw in a CD and the icon for it pops up on the desktop along with a dialog box asking if you want a specific program to use with it. There's no need to search for drives. If it's a music CD, iTunes launches to play it. If you plug in your digital camera iPhoto launches to import the pictures.
If you're looking for a file buried deep inside your Macintosh file structure, you can use Spotlight and it might find the file before you're done typing the first three letters of the name.
Best of luck to you in what ever you decide.
--Rick