This is a fairly cut and dry question that does not require a lot of creativity in terms of framing your response. You should answer by describing the programs or software that you are familiar with. Also, you should indicate the ways in which you have used each of the programs that you have experience using. You might also consider giving examples of the different functions of those programs which you feel you are proficient using. For example, if you are experienced in using Excel you might describe how you are proficient in creating and formatting different types of spreadsheets. Alternately, you might describe your experience using Word and talk about how you have used it in the past to create tables. The goal here is to let the interviewer know which programs you are experienced in using and provide proof that you are really as comfortable using those programs as you say you are.
Also, you should make an attempt to relate your different skills to the requirements for the job. Once again this is where it can be extremely important to make sure that you have thoroughly reviewed the job requirement in advance and found out as much as possible about the prospective job as possible. This will serve you will in terms of framing your response to numerous interview questions, including this one.
You should also be aware of the possible dangers of stretching the truth when responding to this question. It is never a good idea to let the interviewer think that you are experienced in using programs when you have no experience with those programs. Giving a false or misleading answer to this type of interview question will always come back to haunt you. In the event you do land the job the company will expect you to have the skills and experience that you indicated on your resume and in your interview. If you stretch the truth even a little when you are answering this question you could very well find yourself in trouble later on down the road. Always remember that providing untruthful answers on your resume and/or in your interview can be grounds for dismissal, so the best option is always to be completely honest in order to avoid future problems. If you don’t have the experience you think is require you can always say you are a fast learner.