WiFi is an inherently broken protocol, with many specification and implementation flaws and bugs, which have only just started to be fixed (partially) in the 802.11ac standard. But the most serious problem with WiFi cannot be fixed.
Ridiculous contention in an extremely limited spectrum.
If the 2.4 GHz band were a highway, it would have enormous foot-deep potholes every 3 feet down the entire length of the highway, with "Speed Limit 3 mph" signs everywhere, cops from other countries sitting on the side of the road who'll pull you over for absolutely no reason, and enormous herds of cattle who just randomly decide to walk into the middle of the road and stand there for hours for no reason at all, and won't move no matter how much you beep your horn. Occasionally you might meet another responsible driver who's just trying to obey traffic laws and get to their destination.
If the 5 GHz band were a highway, it'd be almost the same, except slightly fewer potholes, and the herds of roaming animals might sometimes be small enough that you can just hit them with your car, kill them, and keep going (if you can stomach all the gore; yech!). Oh, and the speed limit signs might say 25 mph instead.
Because WiFi is so broken, in terms of standards, implementations, and contention, there are probably a trillion different possible variables that could be the reason why your WiFi drops out. To get a sense of maybe 0.0001% of those possible variables, read this article, as well as the followup part 2, at tom's Hardware.
Broadly, the problems with WiFi can be grouped into these categories:
- Something at the physical layer that is unrelated to interference (the actual wifi signals are not reaching their destination often enough to reach the desired level of throughput).
- Something at the driver/firmware/protocol layer (the wifi signals are OK, but some disagreement in the details of the protocol between the base station and the client is causing the connection to malfunction).
- Something at the physical layer that is related to interference from other wifi devices (the other wifi devices may not respect things such as RTS/CTS or other congestion control techniques which can help wifi devices to co-exist, when employed properly and all clients and base stations are compatible).
- Something at the physical layer that is related to interference from pretty much anything else that can emit electromagnetic radiation in the 2.4 GHz or 5 GHz bands, which can include a lot of "non-communications" devices, such as microwaves, vacuum cleaners, DC motors on almost any type of device that moves, and on and on and on. Basically, the way the laws about the spectrum are written, a device is allowed to emit 2.4 GHz or 5 GHz electromagnetic "spam" that has no information content, for any reason, as long as it is contained within the unlicensed bands. Proper EM shielding on the device could attenuate or prevent it, of course, but most microwave oven manufacturers aren't thinking about WiFi when they design their product; they're thinking about human safety, cooking time, and low cost, primarily.
That tom's Hardware article covers the physical interference cases well enough, but you can actually test for WiFi signal interference (from actual WiFi devices, not microwave ovens etc) by looking at a heat map of your wifi.
But that's just getting started. Heck, you may be able to resolve your problem by re-orienting one of your antennas on either your wifi card on your PC, or your router. Or that may make it worse! You might even get better luck by turning your PC, if polarization is at play. Sometimes you might be in a reflectivity dead zone, where the wifi signals are having a hard time finding something to bounce off of to get to the router, in which case you'd want to try moving your PC 6 inches in any random direction (up, down, left, right, pretty much anything is possible). Experiment.
Or maybe just updating your wifi drivers or firmware would solve the problem. Or changing the channel your hotspot broadcasts on.
Who knows? WiFi sucks. Get used to it. The only potential hope for WiFi is the beamforming technologies that are seeing mainstream support (to a degree....) in 802.11ac. But the major wifi implementors have traditionally always wanted to add their own proprietary, "value-added" extensions to WiFi, which almost always create major compatibility problems, not only for their own WiFi network, but even sometimes for other WiFi networks in the area that may be sharing the same spectrum.
Lastly, I will say that troubleshooting questions are bad specifically because there are so many possible things we would have to ask you in order to walk you through the list of problems until you find the one thing that's causing it. You should really attempt to narrow down the problem before you ask; SuperUser is not a "troubleshooting" site. This question is marginal, but I'm not going to vote to close it because it is your first question, and because I hope this canonical answer can serve to help others in the future.