What about my version of Nero? It's really old as you can see. Does that matter?No, that shouldn't matter. BTW, I would recommend burning the media at its rated speed. So, if you have 8x media, burn at 8x. Contrary to popular belief, burning slower can actually result in burns of lesser quality!
If it hasn't already been mentioned, I highly recommend ImgBurn. It's a free, small/light-weight app that I use for burning all my DVDs.
I too recommend
ImgBurn. It is the best ISO burning program I've used, and I've used a few.
Burning your media at different speeds may or may not improve the quality of the burn. As gr33dy mentioned burning slower certainly does not always mean a better quality burn and indeed can be worse. That doesn't mean however you will get the best burn at the medias rated speed.
For example I have two burners that I use and both handle identical media differently. My BENQ 1640 is great with burning most single layer media at or even above its rated speed. It is rubbish at dual layer though. My new Pioneer 111L is great with my dual layer 2.4X Verbatims, burning them with better quality at 4X than their rated 2.4X. The single layer media especially the TDK 16X -R I have burns a lot better at 8X in the Pioneer.
So different burner, different media, different speeds can all make a difference.
I recommend trying your media with the same ISO at different speeds and see what works best. Media is so cheap now it's worth the time and duplicate copies to get it sorted.
If you post what type of burner you have then I (or others) may be able to give you an idea on good media and burn speeds for it.