Cannot delete files

Last night I went to bed and I had like 400 gigs left on an external hard drive. I wasn't downloading anything when I went to sleep. When I woke up, I had a balloon telling me I had "very little disk space" come to find every folder and subfolder were filled with files with names like "~A^8GFBJ.IOU" some files have names that are super long and those one I cannot delete. They all start with "~A^" and when I search that in my hard drive I get 146,356 files. I've downloaded a couple programs to delete locked files, but I don't think they are locked because "FILEassassin" says "Cannot delete the file name is invalid."

I've been searching Google for the last 3 hours and nothing comes up to the exact thing I'm talking about except using command prompt to delete every file one by one. Which.. is that's the case I'll attempt resolve the issue by lighting my hair on fire.