On my two rigs the WinIO64.sys blocked usage of WinAMDTweak.exe by blocking the loading of EIO.dll. This persisted even after rebooting. The only way of deleting the file was by booting into safe mode and deleting the SRB 1.8.4 folder.
Winio gets started/loaded on demand when miner starts. When miner is closed Winio gets unloaded but it wont get disabled until windows restart. After restart it won't be active so you probably ran miner again after restart, that's why you could not delete it.