Why put your miner in C:\Windows\system32 directory? If its NOT there, then you have to add directory where you put it into PATH variable, or,
better yet, start it from its own directory
Another problem could be that its not where you think it should be because your AV erased it
But is in my Download folder and Antivirus is off?
If its in your downloads folder, then why youre starting it like C:\Windows\system32>PhoenixMiner.exe
It should look like C:\Downloads>PhoenixMiner.exe or more probably C:\Users\(put your user here)\Downloads>PhoenixMiner.exe