If you are not going to reinstall Acrobat X on the "old" computer then choose deactivate permanently.
If you think that you might put Acrobat X back on the "old" computer at a later date then choose suspend activation.
Note that the EULA permits two installs provided that only you use the application and then only use it on one box at any given time.
To place Acrobat X onto the "new" computer you will need your CD/DVD and the full serial number.
If you obtained Acrobat X via download you will need to be able to provide the download's serial number.
Hopefully you registered the application and provided the serial number. If so, the serial number is available under the Adobe ID's account that you created.
Regarding the "new"computer. Installing Acrobat X will cause Acrobat 9 to be removed.
Be well...
