No need to use deactivation or activation if you already have BS on one OS and want to dual boot with Win 7. I got this tip from Wombat.
"You may be able to do it without using any activation or deactivation (e.g. totally free). Try using regedit in your XP install to export the key HKCU\Software\Eagle Dynamics\Black Shark to a .reg file. Then, load that file in Windows 7 before you run Black Shark. There is a reasonable chance that it will work.
I have not tried with Windows 7, but I have done this between Vista 32 and XP 32, and it works fine. Also, as a suggestion, to increase the chances that that Starforce will not see this as a "new" PC and require reactivation, I suggest making your machine name is the same in both XP and Windows 7."
I tried it and it works just fine. Make a reg file and put somewhere where you can access it after booting into win 7. Name the computer the same as in your XP/Vista OS when you install Win 7. Then Install BS as adminstrator, then run the reg key. Start BS and voila, no SF activation. You can still run BS on both the old and the new OS. For me BS runs really good with windows 7