I cannot delete a file called AUX.BAT or COM1!

A. A file of which the name (or a part of it) is equal to a DOS devices (NUL, COMx, AUX, LPTx, PRN...) cannot be deleted with Explorer or the usual DEL syntax. Use DEL \.drive:pathAUX.BAT instead (replace drive and path with appropriate values). (The files may be the remains of a failed installation, you can create them e.g. with COPY some existing file \.drive:pathCOM1)