Amateur tip

    'Cause "pro tip" would be more than a little of an exaggeration. However, I did figure out something about Windows Phone again about $20 late. Although there are few Windows Phone users and nobody I know (as far as I know), this might be useful for other phones. For all I know. (Like I said, I'm an amateur.)
    The big problem with the phone was that storage space had filled up. My brilliant and earlier reported observation that this is a Windows Phone and thus the reason I couldn't find any app to manage files on it was because I was supposed to use Windows for that was only so useful. Because a major contributor to the storage space problem was temporary files piling up to the tune of more than a gig. They don't show up in Windows. There's an app on the phone that allows me to dump temporary files, or try, but it never works. Under search settings, there's also a place where you can delete your searches, but that doesn't reduce the quantity of temporary files either.
    Last night, as temporary files started getting up towards 2 gigs, the phone started grinding to a halt again. It turns out that one of the default settings for search is to let Microsoft store your searches, search terms, etc. If you uncheck this and then delete your searches, le voila, your temporary files pile suddenly gets markedly smaller. Still large (225 megs, as I recall), but much less. If I'd known this, I wouldn't have really needed the microSD card I just bought. It still helps, of course, especially in the longer run. And again, I'd feel like an idiot except that the pro at T-Mobile (the manager, I'm pretty sure) didn't know it either. So if this helps anybody, good.