HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Services\ W3SVC\ Parameters Filter DLLs="C:\INetSrv\Scripts\SDK\UpCase.Dll"
Like any ISAPI Filter, this DLL is loaded when the http server is started and it stays loaded until the http server is stopped. Errors in this DLL can hang the server. The http server can be stopped via "net stop w3svc", or you can use the tips in readme.txt in the SDK to run the http service as an interactive process for debugging.