Hello,
Here is a link about upgrades where you will find information about upgrading
http://www.dnnsoftware.com/wiki/upgra...Extra tip: I happened to have done an upgrade from DNN5 to DNN8. I would recommend you don't upgrade directly to the latest version (personally I had issues when I did that). What I did and worked is that I upgraded to the latest version of my current version, then to the first version of the next version and then to the last version of the next version. To explain it better, in your case I would do this:
1. Upgrade to the latest version of DNN 5
2. Upgrade to the first version of DNN6
3. Upgrade to the last version of DNN6
4. Upgrade to the first version of DNN7
5. Upgrade to the last version of DNN7
6. Upgrade to the first version of DNN8
7. Upgrade to the last version of DNN8
At each upgrade check for errors during the installation and in the event viewer and keep backups before each upgrade.