Samsung 5.1ch only front two speakers working

patented? not likely.
being limited to 2.0/stereo input? that is a common problem on cheap HTIB (home theater in a box) sets.

in most cases the problem is that they lack any capability to input surround sound. even in the case where optical or hdmi is provided i've seen some cheap units which limit it to stereo only. if you happen to have a system which is limited by this, there is nothing you can do besides use a setting like dolby pro logic to "fake" surround sound from a stereo input. this is often under the "sound modes" part of the menu where you get effects like hall, classical, rock, etc..

in some cases the HTIB does accept a surround signal through say optical but both devices would need to support 5.1 through optical (on pc its often called DDL ((dolby digital live)) or DTS-Connect). another option is hdmi-arc in some cases however be aware that pc->tv->HTIB via arc will result in 2.0 as the pc does not recognize the tv as a surround capable device (windows limitation). pc->htib->tv works fine (if your htib supports surround input via hdmi).

normally its the prior reason of lacking support. if you verify that the problem is a lack of support (does the manual mention anything about surround sound support from aux sources?) then you could always return it and get something that is known to work.

if budget is the issue i often recommend either the energy classic 5.1 take set or the monoprice 10565 which is a clone of the same set. the klipsch hd theater and some boston acoustics or other branded 5.1 speaker sets also arent bad. most can be had under $330. paired with that you would need to buy a receiver. sony makes some decently powered and cheap models that can be had for $200 or below. for about $500 +/- depending on what you get and the prices you find. this is comparable to many medium priced HTIB sets yet you not only often get better built speakers but a receiver (or AVR ((audio video receiver))) has much much more connectivity and is not limited unlike HTIB sets. sure you need to get a BR player but do you really want a BR player built into your home theater where if it breaks you're only going to have greater issues down the line?

now that does not mean all HTIB are bad. there are some sets which come with a separate AVR (like above but they pair it all in one big box with speakers and everything else), sometimes a dvd/br player and all the speakers and such for one price. sets like this are the same thing as above but do all the pairing for you. some are good some are acceptable. there are also HTIB sets which use the combined dvd/br + amp like the cheaper limited sets which DO NOT lack 5.1 input. while of course having a combined box is not ideal having a set which includes 5.1 input is not as limiting and might work if that is all you can get in your locale.