NIS 2011 re-installing a 4th time

I have had major hardware problems with my computer.  Due to bluescreens and crashes, I have had to install my NIS 2011 3 times previously.  I have just recently replaced my hard drive and power supply. I can't activate my NIS 2011 now due to the number of times I've had to reinstall. What can I do to correct this without purchasing a new activation?