Hi, Welcome to the Forum rodis !
Here are all important links:
http://lmms.io/forum/viewtopic.php?f=1&t=4740
-A few rules and useful forum instructions
First and foremost!
What site are you trying to get LMMS from?
This is the only site, you should use!
https://lmms.io/download/#windows
We also recommend that you get a RC7 version (orange buttons!)
If you already did use our own site, then My guess is that you are using Google-Chome as browser?
If so, you should simply just install Firefox, and try to download again.
Google-Chome can act this dumb way, on some domains, and i have really never figured out why, i just emediately uses Firefox :p
Let us know the outcome :)