In a way, "this general office laptop" is referring to a collection of thousands of laptops, all the same kind. But in another way it is referring to "This _kind_." This one kind of laptop is basic and dependable.
Either way, the subject of the sentence is "this laptop," and grammatically it is singular, so we use "is."
These two sentences are both correct and mean the same thing.
"The Dell Inspiron 15 is a good laptop."
"Dell Inspiron 15s are good laptops."