A few months ago I got myself a Dell Axim X50v, convincing myself that it was a "good investment" as I'd be able to look into developing for the Pocket PC. In time-honoured fashion, I've never actually managed to get past a quick "Hello World" program on it, although I did think it was pretty cool the way you could just hit F5 in Visual Studio and up came the app on my PDA.
Anyway, I just decided I'd give it another bash with Visual Studio 2005 (Last time I tried I was using 2003) and upon hitting F5 I got the less than useful message "The configuration data for this product is corrupt. Contact your support personnel". Fortunately, Google is here to save the day again, and I found a post on a message board somewhere saying to close down Visual Studio, delete the directory C:\Documents and Settings\<localuser>\Local Settings\Application Data\Microsoft\CoreCon, and then restart and try again.
Did the trick for me, and I hope it works for you too if you find yourself here on a Google search of your own.
I get the impression that this folder is/was an artifact of an old beta install of VS2005 although I don't know that for certain. If anyone knows for sure where it comes from please do feel free to enlighten me!