Are you sure this DLL file has been on your PC before you switched into Clean PC Mode and it isn’t modified or recreated while you start/use VirtualPC? I scanned my PC and I did not find this DLL file on it although I had installed Virtual PC. What reminds me about an issue I reported a while ago which in fact wasn’t the issue at all but intended behaviour of Defense+. One of developers explained it, here is a quote and the link to original thread.