What's the deal, then, about upgrading from Win XP Pro to Win7? Is it a heroic task to get Turbotax to operate under 7 when you have legacy files from XP to deal with? Last I heard, you almost had to upgrade to Vista first . . .And is the sys overhead worse on 7 than on XP? Considering that you could presumably get away from using ZoneAlarm with 7?
I hate antivirus software, almost as much as I hate viruses . . .(My inquiry is for a relative; I myself am using an iMac . . .)
It's a from-scratch install of the OS, re-install your apps, and then use their Migration Tool to move your data from XP to the Win7 environment.
It's a great time to get a new/bigger hard drive. Leave the old XP HD intact and bootable; you never know what you might forget in the migration and want to go back and get.
Nearly all modern (last few years) application software that ran on XP will run on Win7 as-is; there are a few exceptions where you'll want to upgrade to the latest release for best compatibility.
Older software... I've got programs written for Windows 95 and Windows NT4 -- the original releases -- that I needed to run as-is because later releases didn't happen. Most run fine. I found one whose installer was 16-bit and wouldn't install under Win7-64bit although it installed fine on Win7-32bit. On a hunch, I copied the resulting installation from a 32-bit Win7 to my 64-bit Win7, and it runs fine -- only the installer was incompatible.
If you get one of the higher-end versions of Win7, it comes with a free download of a Virtual XP machine -- a complete new copy of XP that runs "inside of" Win7, for any programs that really need XP. Best of both worlds.
I find Win7 runs better (faster, more stable) than XP.
I installed Windows Security Essentials (Microsoft's freebie anti-vir) and like it -- it's very unobtrusive.