Open 'Device Manager,' right-click the network adapter, click Properties, then the Advanced tab. Now, in the list of features, find the one that allows you to use 2.4Ghz, 5Ghz or both, and make sure "both" is NOT selected.
When "both" is selected, a lot of adapters will decide on which one is the best option to choose and may often switch between them, thus disconnecting the network connection in the process. Obviously, this shouldn't happen, but it can, unfortunately.
If you care about which option to choose, 2.4Ghz is the slower one that allows for longer distances, whereas 5Ghz is faster but has much less range.
5Ghz may not be supported by your router as it is newer, but it should match what ever your network is set to. 2.4Ghz if you're not sure.