Here's something to try- get an evaluation copy of VMWare Workstation. Get the Fedora Core 2 (or Suse, Mandrake, etc, pick one) CD images, and then install Linux in a window. Try and get it to do everything that you do on a semi-regular basis. If you can, then install it for real.
If not, try a different distro. Repeat until fed up with Linux and go back to Windows, remembering to use Firefox/Opera and Spyware Blaster.
If you succeed, remember that you can always run VMWare under Linux- so you can even run that killer Windows app that you can't with Linux.
Most importantly of all, try and enjoy learning about it- if you get frustrated and p!ssed-off, you're more likely to chuck it in the bin and give up.