Basically:
COM1 is clearly visible in Device Manager but has disappeared from the printer ports list. This prevents the PC from communicating with the receipt printer.
Detail:
I have a PC with Windows 7 Pro connected by serial port to a receipt printer "CBM1000 II". The printer has been configured to use COM1 and has worked fine for ages. User switches on PC next day and cannot use receipt printer. Printer is greyed out in printers list.
Investigations find COM1 serial port is still visible in device manager. it is been enabled/disabled, uninstalled/reinstalled and comes back everytime. It also shows now IRQ conflicts. BIOS settings are correct and can be altered and reset. Investigated the printer config and COM1 disappeared from ports? If try to use the serial port as different com (com2 or com3) in device manager then that version also disappears from the printer ports list AND the highest number com port is renamed by windows. For example, com2 and com3 ports existed in printer ports until we renamed com1 to com2 in device manager. Then when went back into printer ports, com2 had disappeared but com3 and com4 selectable.
Registry has been checked for any obvious issues but nothing sticks out to our level of knowledge.
We're basically looking at re-building the machine. One idea, could the anti-virus prevent the com port from working?
Any help much appreciated!
Cheers,
Clive