Me no worries, I use a MAC.
You do have worries. You just have fewer of them because your not using the platform used by 80% of the users out there, which is PC and Internet explorer. There are plenty of viruses coded for Mac, but the proliferaion is vastly slower-because people who code these things want bang for the buck, it just makes sent to target a larger audience. It has little or nothing to do with Mac being superior or inherently more secure (I am not saying anyone said this here, I'm just making that clear)
Though not impossible, it's pretty unlikely that you receive a harmful virus just being connected to the Internet. I've been an Information Technology consult for the last 15 years, and I can tell you it's usually from visiting a site or downloading a something that you shouldn't be downloading anyway. However, the complications arise because it the past few years, malware and viruses have infiltrated seemingly "trusted" sites.
Wildhorse- There's a popular program called Spyware Terminator (you can get it for free at download.com) that's integrated a feature called Web Security Guard which essentially warns you when you're visiting a site that has been reported to infect with Malware or viruses of any kind. I've found it pretty effective and at least that way your wife will know when she's potentially subjecting your PC to risk.
Bottom line, most virus are annoyances more than destructive (that didn't always used to be the case- 15 years ago people seemed to get mindless pleasure from destroying your data). Now, they are created for a host of other reasons that are too wide and varied to detail here.
It's also correct that no one virus scanner catches everything, so I typically run a few when I am using a PC that I know will be accessing a variety of Internet sites (particularly when accessing questionable sites to begin with, such as Limewire).
Back to the original question, I have really only used FL Studios, which is more geared toward Hiphop and electronica, but I got it free from a friend, so I am not sure I can recommend it as highly for acoustic intruments. They demo'd a few for me at Guitar Center, and I thought Abbleton looked pretty easy to use.