I had (well, still have) Skype Portable 18.104.22.168. It was nagging me to upgrade, but I always let PortableApps upgrade the apps, so I ignored Skype's request at first. But PortableApps's Apps->Check For Updates did not report Skype as being one of the apps that needed updating.
After a while I couldn't stand it anymore, so I let Skype do what it wanted to do. Unfortunately it installed a fresh copy of Skype (not Portable) 22.214.171.124, which of course is not what I wanted. So now I have both.
Why isn't the PA platform seeing the same need for an upgrade that the Skype program inside it was seeing? And what should I do now? Fortunately most of the data associated with Skype is online rather than local, so it doesn't matter too much if I'm a bit schizophrenic in my use of the two until this is figured out.