Please Help Me 5/26/15

Alright i got Bitdefender Internet Security 2015. Then decided i didn't like it so i wanted to switch back to Total Security 2014. I still had 32 days left before it expired. So when switching i foolishly hit the restart on my computer. Now i have no anti - virus.

I went to download it again but all i get is picture for couple secs with a uninstalled bar with 0 % and installed bar 50 % then this message appears '' The exception unknown software exception (oxc0000417) occurred in the application at location (0xda19fc5c)''.

Please help me fix this problem i created.