I use Apple computers myself but you can run Microsoft Windows XP on a Mac using Microsoft Virtual PC. It is amazing to me that Microsoft left the Firewall open in Windows operating systems. That is like leaving your door unlocked when you go to work so that you will not have to unlock the door when you get home. The Microsoft Windows XP Service Pack II is supposed to close the Firewall, but you can also do this yourself.
From what I have been able to find out, you can make Windows XP fairly safe by using the Mozilla browser instead of Internet Explorer (which has Active X and sneakware, adware, and spyware can be added just by visiting a web site). There are some freeware anti-spyware products like Ad-aware and Spybot. You can even get free anti-virus scans at Trent Micro's Housecall. But using Windows XP Professional in Virtual PC on a Mac is one thing compared to searching the internet with it. Better to search with the internet with the Mac.