265T unresponsive

MY GPS was fine until I left it plugged into PC overnight as I had done in
the past. In the AM it just had a whitish screen . I powered it off and -
never came back on. My question : how to tell if " just a battery problem"
vs. electronics failure ?
Just wondering if worth buying/ trying a replacement battery.
I do ( did) like it vs the newer models which are too big for the spot I
have in the car.

Also I backed it up periodically to PC ( copied current.gpx) but now notice
that the date on the PC file shows 2009 for all versions ( I saved in
different folders on different PC's at various times). Is that right - that
even though I back it up in 2011 the modified date shows 2009 ? ( files are
different sizes so they are definitely different. I usually notice stuff
like that but have been on the road for 9 months and just now returning home
to my own PC's - to try to salvage the gps.

Worth my effort / battery cost ? - or just buy another one ?

If I get a new one, can I "import" my saved favorites ?
Thought I'd copy new gpx file to disk ) just in case) then overwrite it with
old gpx file - is that right ?