Thank you mjashby! It doesn't seem to be a CD/DVD driver problem.
I have Windows 7 and a netbook. It used to work okay. I thought that -- when this problem started -- I previously restored my Windows to an earlier point in time to try to fix it. But last night, I tried to restore to an earlier restore point and wasn't able to do it. it said that an anti-virus program might be interfering, but as far as I could tell I deactivated my anti-virus programs.
I don't seem to have Windows 7 on a disk, so I can't reinstall it. I think I might just upgrade to Rootsmagic 7 and see if that works for me(?)