I've made clean installation of Windows 2-3 times since I've entered the passwords last time.
I hope the investigation of this case can improve the Bitcoin world and can prevent such incidents in future
Did you transfer any BTC to any address controlled by the private keys in question before this? Or was this the first time you sent BTC to this wallet?
If it was the first time actually using that wallet, it seems likely your private keys were already compromised before you reinstalled your OS. So how secure was your setup before you installed Windows 10? Were you using that laptop for anything other than running a Bitcoin client? When you first installed the client, how confident can you be your system was clean at that time?
I had the 1st wallet. Then when the sum of bitcoins was pretty big I've made the new one (about 3 years ago). I've transfered the bitcoins to the new wallet 1 time and keep them there. For the new bitcoins I've used the new wallet.