Hi Betty,
First off, I'm not sure why having pictures on the hard drive would slow up the operating speed of the computer. Maybe restarting the system may get things back to where they were.
Anyway, yes you can burn them to DVD. This is an excellent idea. It will give you piece of mind, so if your hard drive crashes, you will have copies. Assuming you have a DVD writer, you should have software that will allow you to do it in similar fashion to burning a CD. However, I'm not well versed enough to guide you through it via the bulletin board. If you have a friend or relative who can sit down next to you and guide you through it, you will become an expert at it in no time. Now, what I do, is back up my pictures to CD and keep them at work so if anything should happen at home, I have copies stored safely somewhere else. I also use an external hard drive to back up copies of pictures and documents. The nice thing is it does it automatically every day. Had the hard drive crash a couple of months ago and I was glad I had the irreplacable pictures of my family safely backed up. Storage is cheap, having to send out a hard drive to have data recovered is not.
Good luck, Tom.