Strictly speaking the answer is yes. If you use or just install anything that can receive or record television programme services (which includes video recorders, set-top boxes or PCs with broadcast cards) you have to have a TV licence.
Don't panic though! If you don't actually use your PC to receive TV progs the only way they would know your PC was capable of this would be if a TV detector person knocked on your door and asks you (and you then tell them the truth).