I'll put this in the forum to see if anyone's got an idea re. this conflict.
When starting XAMPP on an XP machine that already has Skype running, I then start MySQL from the CP -- it will start running, but when clicking on Admin, the phpMyAdmin screen will not appear in Firefox (rather a blank screen appears, status shows 'Done'). Apache will NOT start, showing only 'Busy' in the CP status windows.
The workaround seems to be to exit Skype, and then restart XAMPP. MySQL and Apache can then be started normally and phpMyAdmin will show itself. I was then able to start Skype and it appears in the taskbar are running normally.
I discovered all this after looking over the Port-Check and seeing some references to Skype in the Status column.
I thought I'd share this as it cost me a few hours. Any comments welcome.