Hi, Paul.
After my bedtime and I really don't get on with these smart telephone gizmos - a few links which might help, though. You might like to download the manuals from the Samsung site (the downloads are down in the second half of the page):
http://www.samsung.com/uk/support/model/GT-I9100LKAXEU#n
There are lots of "solutions" on offer there, too.
A couple of other bits and pieces:
https://www.eightforums.com/drivers-hardware/18035-my-windows-8-pc-wont-detect-my-samsung-galaxy-s2-...
https://android.stackexchange.com/questions/17735/galaxy-s2-not-recognized-by-computer
I'd be inclined to go through the manuals and the Samsung site first, but however you prefer to do it!
You're running an elderly version of Android there, which might not help hugely. Not much you can do about that, of course.
I've absolutely no idea where the dropping signal is concerned. As I say, it's a bit late for me - but you might like to try an internet search if the Samsung manuals/site offer no help. (Would reseating the SIM card - taking it out and putting it back - help? Might be worth a try - it's an elderly device, as these things go, and you might just be looking at mildly dirty/corroded contacts.)
Hopefully someone with experience of your gadget will be along with something more succint.
Let us know how you get on - good luck!
