My neighbor wants to borrow some of my HD DVDs but he only has an upverting DVD can it play the HD DVDs.Forgive my NEWBIENESS

No, it cannot.

Thank you for your fast response

Many upscaling players state HD DVD in their ads (as opposed to HD-DVD), which causes confusion. No, your neighbor will not be able to play your HD-DVDs.

UNLESS, you have a combo disk. He just has to play the DVD side.