If you don't mind upsetting the anti-virus software, you can also inject a DLL into each process that will then hook CreateProcess (to inject the DLL into further processes) and CreateWindowEx (for your purposes).
If you don't mind upsetting the anti-virus software, you can also inject a DLL into each process that will then hook CreateProcess (to inject the DLL into further processes) and CreateWindowEx (for your purposes).