so i have Windows 8.1 and don't have bluetooth on PC... I have Logitech reciever (it doesn't have bluetooth nor unifying logo) connected to PC.. is there way to connect them ? (It's from Logitech M185 mouse..)
While booth Bluetooth devices and and Logitech's receiver operate in the 2,4 GHz band they are not interconnectable. Logitech is using its own proprietary protocol how Mokubai suggested in his comment.
The easiest solution would probably be to buy a simple usb bluetooth dongle. They are available relatively cheap nowadays.