Vista ain't that bad completely patched up. Security-wise, it's better than XP (though a bit slower and with some annoying dialogs). It has some compatibility issues with some older programs though (namely, it's security model is tighter and some programs just won't work when cut off from certain functions that the OS used to let them do). Also, it uses a different driver model now, and since a lot of drivers had to be rewritten from the 2000/XP versions (which had since 1999 to be brought up to spec), there was some initial instability just from drivers.
Truthfully though between a fully patched version of Vista with updated drivers, and the new Windows 7, there's not a ton of difference. Microsoft is mostly pushing out Windows 7 because Vista started out a bit rocky and even though most of the stuff is fixed (well, fixed as much as a Microsoft OS is gonna get
) the Vista name now as a stigma attached to it.
Whatever the case, go grab a copy of Firefox (
www.getfirefox.com). It's a much safer browser than IE. If you want the safest computing experience though, Linux or Mac is the way to go. Mac's take special hardware (ie, you have to buy a mac computer - kinda, anyways. you can make MacOS run on a "regular" computer but it's not a beginner's project) but Linux will run on just about anything you put in front of it. Not much of a gaming OS, but for surfing the web and keeping the machine going it works very well, and it's available free of charge.