I am going through the same frustrations and it is driving me round the bend.
On initial install of WAMP I got the thrid red icon. With a bit of digging around I discovered that it had something to do with MySQL not working and I found that I had an old MySQL service knocking around and so I stopped that service. Bingo - all was well - no red icon.
Firing up localhost prompted for a password and unless supplied it wouldn't work. So I found the info regards how to do this and reset the password and changed my config.inc.php file.
Everything working like a dream
I then set the existing MySQL service to manual, to prevent conflict and restarted the PC - to make sure all fired up as expected.
I now get the YELLOW icon and can't for the life of me resolve the problem. I only have one MySQL service running. I have used a MySQL Server admin tool to stop and start it and can see the WAMP icon changing (to red on stop and yellow on start), so I know that WAMP is addressing the correct MySQL instance. But is still insists that I enter a password when I try and fire up localhost or PHPMyAdmin???
I haven't got Skype running but how do I check what service is using which port? Maybe I do have a conflict but I don't know how to find it.
Thanks in advance