Here is a nice PC application for detecting COM ports. (Comlist)

Using Arduino Interfacing w/ Software on the Computer
1

When working with multiple Arduinos or virtual com ports in windows,
it is good to have something show what you just plugged in.
The last port inserted is shown as "new".

Comlist is free and can be downloaded from http://skjolddisplay.no/?page_id=33

2

Can the source code be downloaded?
Not everyone here just download binaries .....

3

I've attached the source. Hope it can be useful.
Its made with visual studio 2010 in vb.net.

PES Comlist.zip (138 KB)