You will need to remove the CC downloaded app and then download the Lightroom 5.7.1 from here and add your serial number. The apps are the same but the licensing section is different so a whole new app download is necessary.
I would suggest renaming the Preference File (with Lr closed) so as a new one is generated upon opening.
Their location is detailed here: http://helpx.adobe.com/lightroom/kb/preference-file-locations-lightroom-41.html
It was recommended early on to set a preview size the next size up from the monitor pixel width. So go as big as possible with yours RJ.
You may also want to consider upgrading to Lightroom as that may help with speed - maybe!!
Back to hibernation myself.....:grin:
Cletus.... I would say Adobe has given it a lot more thought and research then you and I out together. :razz:
Lightroom Mobile is version 1.0... now think (or research) of what Lightroom v1.0 could and could not do and then consider Photoshop 1.0.... This is the way forward and I am confident...