After the upgrade you will need to apply your activation key. This is found in your customer portal. Here are migration instructions:
http://knowledgebase.solarwinds.com/kb/questions/107/Move+Kiwi+Syslog+Daemon+to+another+machine
Keep in mind that if you are moving from a 32 bit system to a 64 bit system you will copy the Syslogd directory to C:\Program Files (x86) and install to that directory.
You will also want to use this tool to deactivate your license:
http://solarwinds.s3.amazonaws.com/solarwinds/Release/LicenseManager/LicenseManager.zip
This will send your activation key back to your customer portal. Once your key shows up, you will be able to use it on your new system.