Hi JD, thanks for the reply.

I downloaded CGminer 4.1 to windows 7 - inside the zip is CGminer.exe which I run from a batch file along the lines of

@echo on
cgminer.exe -o pooldetails:3333 -u myusername -p mypassword

I've tried adding in the '--hfa-hash-clock 600' on the above string and it causes CGminer to load and immediately quit.

Obviously I'm a moron for not knowing this stuff so really do appreciate the help.