This is a great question. The reality with today’s technology is that it is changing all the time and the world “old” has a new meaning. If you mean your computer is more than 10 years old, then for sure, save your money on this event and use it to go and buy a new laptop, tablet or computer 
But if you are talking a few years old, you should be fine, your camera resolution may not be the best, but then again, you may not need to use it to participate. As long as you have a functioning speaker and keyboard you will be fine. Of course, a good mic and camera will help you get the most of the live virtual event, by allowing you to talk and share yourself with fellow attendees.