What does 'registering' mean? 
Two things: 

1.  To send me your data, so that I could keep a IsiPlot users database, to be able to inform you (if you like) about new releases.
2. To contribute to IsiPlot developing-enhancement paying 10 euro for the license. 

You can use PayPal clicking the botton below:

I have a little problem with international cheques, I have a cost of about 8.5 euro/US$ to cash them.... too much!

If you have 2  PC no problem, I then will send you the registration password for your second  PC. The registration is to YOUR name, and so YOU can have password for YOURS PC. I think that isn't right a thing to ask money for every PC. I think this is the good approach to software distribution. If you have 2 PC you'll use them only one at a time, I suppose!
But please, don't ask me passwords for yours FRIEND!  
If you ask me 20 passwords in a year, I can suspect that you are distributing password to your friends, and I will stop to send them to you.
So this way to manage registration requires that users of Profili are as honest as I'm. Please don't take advantage of this by distributing passwords....

  You can contact me by 

Duranti Stefano 
via della Casazza, 43/B 
32032 Foen di Feltre (BL) - ITALY 
E-mail st.duranti@alice.it / info@profili2.com 

I started also a mailing list named ‘Software Profili’, where all users can exchange opinions, tips and plans. If you like subscribe it send a message to software_profili-subscribe@yahoogroups.com.
The subscription is free.