Start with the present and tell why you are well qualified for the position. Remember that the key to all successful interviewing is to match your qualifications to what the interviewer is looking for. In other words you must sell what the buyer is buying. This is the single most important strategy in job hunting.

So, before you answer this or any question it's imperative that you try to uncover your interviewer's greatest need, want, problem or goal.
To do so, make you take these two steps:
Do all the homework you can before the hr interview to uncover this person's wants and needs (not the generalized needs of the industry or company)

As early as you can in the interview, ask for a more complete description of what the position entails. You might say: "I have a number of accomplishments I'd like to tell you about, but I want to make the best use of our time together and talk directly to your needs. To help me do, that, could you tell me more about the most important priorities of this position? All I know is what I (heard from the recruiter, read in the classified ad, etc.)"

Then, ALWAYS follow-up with a second and possibly, third question, to draw out his needs even more. Surprisingly, it's usually this second or third question that unearths what the interviewer is most looking for.

You might ask simply, "And in addition to that?..." or, "Is there anything else you see as essential to success in this position?:

This process will not feel easy or natural at first, because it is easier simply to answer questions, but only if you uncover the employer's wants and needs will your answers make the most sense. Practice asking these key questions before giving your answers, the process will feel more natural and you will be light years ahead of the other job candidates you're competing with.

After uncovering what the employer is looking for, describe why the needs of this job bear striking parallels to tasks you've succeeded at before. Be sure to illustrate with specific examples of your responsibilities and especially your achievements, all of which are geared to present yourself as a perfect match for the needs he has just described.

There are numerous good possibilities:
Loyalty, Energy, Positive attitude, Leadership,  Team player, Expertise,
Initiative, Patience, Hard work, Creativity, Problem solver

It's up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you're okay.

DLLs, VBX or OCX files being unavailable or in the wrong versions. Applicatioins using say these older DLLs expect some behaviour which is not present.