Remove unused serial ports under winxp

http://support.microsoft.com/kb/315539


To work around this behavior and display devices when you click Show hidden devices:

1. Click Start, point to All Programs, point to Accessories, and then click Command Prompt.
2. At a command prompt, type the following command , and then press ENTER:
   set devmgr_show_nonpresent_devices=1
3. Type the following command a command prompt, and then press ENTER:
   start devmgmt.msc
4. Troubleshoot the devices and drivers in Device Manager.
   
   NOTE: Click Show hidden devices on the View menu in Device Manager before you can see devices that are not connected to the computer.
5. When you finish troubleshooting, close Device Manager.
6. Type exit at the command prompt.
   
   Note that when you close the command prompt window, Window clears the devmgr_show_nonpresent_devices=1variable that you set in step 2 and prevents ghosted devices from being displayed when you click Show hidden devices.

If you are a developer or power user and you want to be able to view devices that are not connected to your computer, set this environment variable globally: 

To have us set the environment variable globally for you, go to the "Fix it for me" section. If you prefer to fix this problem yourself, go to the "Let me fix it myself" section.