unfortunately steam really does honestly prefer to be built into the C:\ drive. i think it is just because of steams security measures and the way they lay the whole thing out. ive heard of issues from steam on other drives before. im not sure what POI means. what format is the drive your installing onto? and how big is it whats it labelled as? a fresh steam install would need to be on the drive first and copying and pasting current file contents from your C:\ may cause the issue was well. everything on your new drive will have to be freshly installed and two instances of a log in could also conflict things as well. its a vast ocean topic my good sir