I keep my Windows system as clean as the first snow. And, maybe you can, but as security writer, Michael Horowitz, said, "In my opinion, while it is possible to secure a Windows computer, the process is too hard, too time-consuming and/or technically over the head of most people." Therefore, unless you're an expert who puts the time in to keep your PC safe, he recommends that you should "consider instead, Macs and Linux, my preference being Linux" for your online finances.
Get the point? It's not safe else there on the big nasty Internet for your Windows PC. Windows 7 is filled with improvements, but security isn't among them. As several of these people point out, it's not like you have to give up Windows. You can use live Linux CDs for when you need to go shopping on Amazon or the like, and then return to your comfortable, but not especially safe, Windows.