Hi - sorry to hear you're having trouble with ANTS Performance Profiler.
There are a few things that can cause IIS to misbehave and return a "could not start" message - have you tried any of the tips in our article on troubleshooting IIS profiling
? A good first step is to check that the account you're specifying has read access to %ProgramFiles%\\Red Gate\\ANTS Performance Profiler7\\ProfilerCore.dll
If you've tried our new continuous profiling beta mode, you should also try uninstalling that, as the early access version of this tool currently conflicts with IIS profiling from the main Performance Profiler interface.