Thank you JV16,
Yes, I have two PowerTools 2009: for Vista, I bought a license which was downloaded to a Jaz disk. Then I installed the file in the JV16 folder. For XP, I copied the license from the Jaz to a floppy disk and, then, I copied it from the floppy to the JV16 XP folder. As you write in your mail, I attempt to "Install a new license", finding it in XP JV16 folder. But the answer is: (I translate from french ! ):
The following license file was found: C:\Program Files\JV6PowerTools 2009\License.xbin. however it is not a valid license file for JV16PowerTools. Error message: license file not valid or corrupt. If you have bought a license, please contact Macecraft Software for a new license."
Could you propose a solution ?