Mahmood,
if you have some problems with Delphi and
BCB components, it's a better to search in Borland community.

1.did you try to search MERS:
http://www.mers.com/searchsite.html or
http://www.tamaracka.com/search.htm
2. Did you try to post your question to the Borland Newsgroup? You can choose advisable group and post your question there. I use Outlook Express as Newsreader. See here:
http://info.borland.com/newsgroups/

I create serial comm handlers directly under Win32API and if I want to change COMx to COMy during program is in progress and it is necessary to safetly close all openned handlers. Clear all buffers, finish communication, close handler, terminate and delete all threads ...
BTW: Do you use Sync or Async methods in your apps and do you WaitForAsync in case you use async functions?

Vaclav