>I currently have an XP, so I'll be buying a new pc very quickly. I've been advised to go to Win 7 instead of Win 8 as it's easier to learn.
>I want to make sure however that all my old VFP .exes will run on 7. Are there any problems in that regard? Also, which version of 7 is recommended?
>Home Premium? And what about 32 vs 64 bit? Any problem running the exes on either?

If you're a dev I'd go 64-bit, with minimum 6GB RAM (if triple-channel), 8GB otherwise. Consider 16GB if a prospective machine supports it. One drawback is that won't natively run 16-bit FPDOS 2.x or FPWin 2.x programs, if you need that you'll need to set up a virtual machine and install a 32-bit Windows OS on it.

Solid-state drives (SSDs) for at least the boot device are highly recommended these days.

There have been zillions of valid complaints about the Windows 8.x UI for conventional desktops or laptops. It looks like MS is finally addressing most of them: http://mashable.com/2014/04/05/microsoft-windows-8-retreat/ . So, if you can wait a bit, or tolerate Windows 8.1 as it is now without those improvements then Win8 may be your best choice.

When I called Dell Small Business a couple of weeks ago to get a couple of new machines for a client, they pushed real hard to make them Win7. The cost of training and loss of productivity during refamiliarization is higher with 8 and may be hard to justify for businesses with lots of seats or that are time-pressured. And especially if they're resistant to change. But, if you're a dev with a single machine and you're willing to suffer a little while you get up to speed, Win8 is probably more future-proof. It also keeps you familiar with 8 if you think you'll need to support that for your clients.

Another option if you have a husky Win7 machine would be to run Win8 in a VM. That way you wouldn't need to run it all the time, only for testing (VMs are great for that). With Win8 Pro or higher you get Hyper-V which is a good VMM. There are others available for Win7. Or run Win8 VMs on Win8 :) (almost too many possibilities)

Yet another variable is Microsoft is ending sales of all versions of Win7 except Professional on October 31, 2014: http://www.pcworld.com/article/2105765/3-ways-to-get-a-new-windows-7-pc-in-the-windows-8-era.html . So, that will tend to force the MS world to 8.x.

Interesting times.