Problem solved (but still wondering why CD/DVD wouldn't write). Followed advice given previously on this post. PC all cleaned up with CCleaner, backed up with Macrium, any issues resolved with Tweaking, and protected with Microsoft Security Essentials. Removed all trace of iOBit software. Also using Malwarebytes AntiMalware as well as SuperANtiSpyware (I had been using these previously). Some redundancy perhaps, but overlap is better than gaps, right?
Next step - since I really didn't want to wipe my PC and reinstall everything, even with a backup image, I opted to replace one of the DVD/CD drives. This not only provided me with one good one, but the 2nd original DVD/CD drive is now behaving as it did before (meaning I can read and write with it again). Could one bad drive cause the 2nd one to 'fail'? And if so, it was just a 50/50 chance that I replaced the culprit - i merely removed the top one, there was no logic to the decision. I just figured I'd end up with only one good one anyway (the new one). So.....who's answer should be accepted for the resolution??
Again, thanks again for everyone's help. Very glad to have stumbled upon this site - everyone is great!!