I haven't checked back at this thread for a while, seems it has taken off....
It's true that a lot of people have a lot of problems with Windows, but it is possible to run an XP computer problem free for years. I have nine computers networked in my large household and they are mostly trouble free. Most of my customers go years without trouble after I set them up. It does require being careful what you click on, there is no antivirus that can help without that.
Macs do offer 'security through obscurity' but are far from problem free. I fix (and have built on PC hardware) macs also and a major problem with a Mac is a bigger deal generally than with a PC. You will find it harder and more expensive to find help fast. You cannot run many programs. You cannot use many peripherals or upgrade hardware easily. It is harder (at least knowledge and tools are less common) to recover data.
And at the end of the day, most trading software just won't work, or if you find one that does you are stuck with it because alternatives won't work. Forget Mac - unless you have software you are 100% certain you will use for the life of your computer.
Here is a pretty good article on the subject:
http://keznews.com/5061_Six_reasons_OSX_will_not_go_mainstream (Warning: rude ads sometimes...)
Somebody mentioned the lack of email scanner in the free Avira - this is not a problem but a bonus. Email scanning is worse than useless. If this sounds mad, read this before deciding:
http://thundercloud.net/infoave/tutorials/email-scanning/index.htm
P.S. In addition to Avira AntiVir Free (from
www.free-av.com) I am now recommending the latest 1.6 version of Spybot (from
www.spybot.com) as problems appear to be ironed out. Untick all options while installing except for a desktop icon and start menu entry. Manually scan weekly or as often as you like.