Hi Russana, clearly you have used multiple emai addresses in the past.  I do too, but I use one  for things like trials (so I don't get all the spam associated with a trial) and one for things I buy.  You are going to need to go back in your records (hopefully you do not delete important emails like registration confirmations) and try to figure out which one you used.  Hopefully you still have the confirmation, if not you will probably need to contact Magix sales or possibly Magix support to get their help to find what address you used, using your serial number.  No one here works for Magix, so we can't really find that for you.

Good Luck,

George