This is nonsense. The drive in question is just 35 % full and has 304GB free.
X1's folder "C:\Users\...\AppData\Local\X1 Desktop Search" has just 4GB of stuff.
By the way, can someone make that error message more explicit? I had to confirm that it really was an X1 error by launching the program and seeing what happened. The message could refer to anything else that indexes.
