Thanks Mark. I think I've concluded that it is caused by me doing my own compiles using VC++ 2012 (aka 11.0). Without having SP1 installed XP is not supported as target system. I've tried to install SP3 (which is the latest available, can't find SP1) but when I try an online install it complains about some missing root certificates, and when I try to download the ISO it always gives the wrong SHA-1 value. So I've given up on that. And at the moment I don't feel like taking the risk of reverting to 2010. I leave it for now and attack it if and when necessary.