The Picasa pictures are on the "cloud" which means they're uploaded to a server, they're not physically on your devices and no matter what you install on your device they will only be there unless you download them.
To get them on your PC login to Picasa in your PC and download the pictures. Or login to Google+ on your browser, once logged in, hover the pointer over Home and select Photos. You can actually do this from your devices now. In your app draw, look for G+ Photos and open the app. You'll be taken directly to your uploaded photos. Here you can edit, download or delete your photos.
Hope that helps.
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