LTCD ist the first coin i invested in (200k Coins) and before i only used Bitcoin on Blockchain Online Wallet
Maybe a stupid question but if i Transfer my 200k LTCD from Bittrex to the Windows Wallet.. what happens if my PC crashes or something? Are the coins lost then?
Tank u if somebody could answer this newbie question

You should back them up else where just in case. Just type %appdata% in the search programs and files box and then look for the LitecoinDark folder. There will be a file called wallet. Just back that up to another computer or storage device and you're good.