Chaps,
Sorry for the late reply, but minutes after I posted last night I heard a tink ... tink ... tink noise from my spare machine and the HDD died, but luckily it only took about 8 hours of AVI files with it, which I can convert from DVD again. This morning with a fresh mind I checked the following: * ASP.NET 4 32 and 64 bit are allowed in IIS. * I've run ServiceModelReg -i from 32 and 64 bit framework folders. * I've run asnet_regiis -i from both framework folders. * I fiddled with folder permissions. * I set the service to use the classic 4 pool with NETWORK SERVICE as the default account. * I wrote a "hello world" service and set custom errors off and include exception details to true. * I wrote a console app to call the service. Despite all of this, my console app calls the simple service and still gets nothing but 500 Internal Server Error. The last time I saw this error on Win2003 it was caused by SVC being unknown to IIS, but I think I've run the right steps to overcome that. I'm out of ideas. I've now spent 4 hours trying to get a "hello world" service not to return 500. Greg
