Hyper Threading (HT) acts like virtual cores. Not as good as having an actual core, but better than nothing. Programs must be designed to take advantage of HT, otherwise there is really no performance gains. If both cores in the Core i3 are busy, then the Windows background programs should at least be able to take advantage of HT.
Programs designed to make use of HT can generally get a 10% - 40% boost in performance if they are designed to use HT and it also depends on how well that ability has been integrated into the software's design.