Probably you installed SendBlaster 2 after formatting, but the license key you purchesed is valid on SendBlaster version 1 only.
The licence key of version 1 will not work on SendBlaster 2.
If you bought Sendblaster after July 1 2009 you are elegible to get a FREE upgrade to SendBlaster 2 Pro: https://www.sendblaster.com/freeupgrade/upgrade.htm
Otherwise you may:
1) Continue using SendBlaster 1. You can download it here: https://sendblaster.com/download/sendblaster163.zip
2) Buy the upgrade to version 2 here:
I reinstalled my office computer and because of that also reinstalled my copy of SendBlaster Pro. Now I can’t upgrade the “Free Edition” to a “Pro”. Please help!
You probably registered your copy of SendBlaster and now you’re entering the registration code instead of the license key.