mIRC License Agreement: mIRC is shareware, which means that you can try it out freely for 30 days to evaluate it. If during, or at the end of, the evaluation period you decide that you would like to continue using mIRC, you must register your copy.
It does NOT indicate anywhere about being limited to a single installation instance. The license agreement transcends such petty attempts. If you were to switch brains or have a serious case of amnesia, that argument might hold some water.