I have Labtop HP with four USB conectors. Use Windows 7 Ultimate. I use Usb to Serial adapter. Some programs can use only port's COM1, COM2, COM3 and COM4. Unfortunatly they are in use. For COM1 and COM2 I know that are used by PLC programing devices, but COM3 and COM4 i do not know who use. How can I see who use them, and if I do not need those devices, how to release them to assosiate to USB - serial adapter.?

In many cases aditionnal "virtual" com ports are used by for example bluetooth adapters. You can check the status of the COM ports in device manager. However, whether you can configure the port depends on the driver used. Another possible cause might be that the program needs administrative privileges to run. Right click you program and choose "run as administrator" to test this.MCP/MCSA/MCTS/MCITP

I know which ports are used by bluetooth. And the programs I run are made like that and I can not change them. In device manager I can see used ports, but I can not release them. For example, I want to replace the port fot USB - Serial from COM22 to COM3, but it is marked that the COM3 is in use. I do not now what devide use it, probably some device attached to uSB some months ago, and is not more in use. I do not need this device and I want to release COM3 fromuse and assosiate it to USB - Serial adapter. Anyhow, thank you for advice

Hi skocev, you can try to uninstall the driver of port COM3(right click “Computer”-----Manage-----Device Manager-----Ports(COM&LPT)-----select COM3 and uninstall it), and scan for hardware change(right click “Computer”-----Manage-----Device Manager-----Action-----Scan for hardware changes) to check if this port still in use or not. We can also open System Information to view all hardware configuration, type: msinfo32.exe in the Start Search box. As you want to know which program occupied the COM port, it seems should use the third part tools to scan. Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi, One basic question I want to ask, because in your query it is not mentioned. Do you have 4 physical COM ports in your Laptop? If your answer is no, then you are trying to use the virtual COM ports. Then the USB to Serial driver should co-operate with you. Moreover its all depends on your USB to Serial driver. -AJ

I can not unistall the driver because it is not shown in device manager if its devicis is not present on USB port. I do not have phisical ports but only four USB inputs. Thank you for your answer

O.K. I found solution. Solution is to show hiden devices in device manager. Thank's to everibody