So if you just really have to uninstall BI4 here is the way I did mine successfully.
1. FIRST and most important. Run regedit and navigate to this key and export the key to a safe folder that you can find again later.
2. Now uninstall BI4
Be sure you select NO on this one...some people say this works, it did not on 2 of my systems.
Now if all works well, BI4 will be uninstalled and you can see if BI5 will run. If all looks good then you are DONE
BUT if your BI5 loses any settings or won't even run then continue on to step 3.
3. Open regedit and navigate to the Perspective Software key. If you see this folder you will need to delete it first. You will need to change permissions for that key and then delete it and then you can delete the entire "Perspective Software" key.
Then you are ready to import your exported file we did in step 1. Just dbl click that file and it will import it back. DO NOT use BI5 import feature.
I also recommend using BI-updatehelper as this will backup up your registry on every update. Get it here:
Blue Iris Update Helper (BiUpdateHelper)
1. FIRST and most important. Run regedit and navigate to this key and export the key to a safe folder that you can find again later.

2. Now uninstall BI4

Be sure you select NO on this one...some people say this works, it did not on 2 of my systems.

Now if all works well, BI4 will be uninstalled and you can see if BI5 will run. If all looks good then you are DONE

3. Open regedit and navigate to the Perspective Software key. If you see this folder you will need to delete it first. You will need to change permissions for that key and then delete it and then you can delete the entire "Perspective Software" key.

Then you are ready to import your exported file we did in step 1. Just dbl click that file and it will import it back. DO NOT use BI5 import feature.
I also recommend using BI-updatehelper as this will backup up your registry on every update. Get it here:
Blue Iris Update Helper (BiUpdateHelper)