Thank you for your answers.
If Securom doesn't get installed until you run the original .exe then I think it's best to remove it now, I don't think I'm ever going to want to play Mirror's Edge online, and I don't play it all that often anyway, so it doesn't matter, I'll just disconnect the internet when I play it to be safe.
The only problem I have now, is getting the no-CD crack,
this is the Mirror's edge page at GCW, I've never downloaded anything from there, so I have no idea which one might contain the no-CD crack. Help?