Try Team Red Miner, this miner is one of the best for AMD video cards and it has a version for windows
https://bitcointalk.org/index.php?topic=5059817This miner has a reduced commission for video cards with a Polaris chip.
What AMD drivers are you using?
What is the size of the virtual memory file? You need to install at least 16 GB.
Don't mean to degrade this teamredminer but it performs very worse for me compare to other miners, maybe it's because I'm using from nicehash software? I could be wrong but it's pretty bad inside nicehash, hashrate is very very low compared to phoenix miner