No and HD DVDs are discontinued
No, regular DVD players can not play HD DVDs. We need an HD DVD player. - Neeraj Sharma
No and HD DVDs have been permanently discontinued
HD DVD and Bluray are both high definition disc formats but they were not only competitive formats but incompatible formats as well. While the battle for the HD market was in progress a handful of players were sold that would support both formats. These players were expensive and very few were ever sold. Unfortunately, HD DVD only players will not play Bluray and Bluray players will not play HD DVD discs. It is still worth keeping HD DVD players as they are the only players capable of HD DVD discs.
Yes they will
Yes the Philips DVD Player with HD Upconversion.
HD DVD is a high definition disc format that was competing with Blu-ray discs when they were first introduced. HD DVD lost the battle of the formats and is now obselete. The only players that will play an HD DVD are dedicated HD DVD players and they are rare players these days. Standard DVD players and Blu-ray players are both incompatible. It's almost certainly easier to buy Blu-ray discs than to find the right player but they may be available on auction sites or trading sites.
Bluray and HD DVD are the two trade names for high definition discs and players. Bluray is by far the better choice for the simple reason that HD DVD was withdrawn in 2009. Bluray had won the HD format war so HD DVD quietly left the stores. There are a number of HD DVD discs around as well as the players. As the two systems are in-compatible, don't trash your HD DVD player just yet. It will still do a do job of playing the HD DVD discs you still have.
No and HD DVDs have been permanently discontinued
There are three storage formats for video discs: A DVD will carry standard definition video and will be described simply as "DVD". DVDs can be played on standard definition DVD players as well as either of the HD disc players mentioned below. Regardless of the player used, the image will always be standard definition. HD DVD is one of the two HD disc formats. The disc will be described as an "HD DVD". This format was withdrawn in 2009 when Bluray won the HD format war. HD DVD players and discs are still around but none are sold commercially now. These discs can only be played on HD DVD players. Bluray is the other HD video disc format. They will always be described as "Bluray". They can only be played on Bluray players and will not operate on standard DVD players. Nor will they play on an HD DVD player. Note: HD DVD is the product trade name of the now defunct high definition disc format. It is also commonly used in reference to an disc that supports high definition video. Therefore, is it sometimes used as a reference to Bluray. Although Bluray is a high definition DVD, it is NOT an "HD DVD". As the HD DVD format moves into the history books of television, the term is used more and more to refer to Buray even though it is strictly not the correct term.
The introduction of high definition discs saw two formats launched. Bluray is one and HD DVD was the other. The format war was won by the Bluray system and HD DVD was withdrawn in 2009. Both Bluray and HD DVD are high definition players but note that "HD DVD" is the name of the format and is confusingly close to the generic description of high definition disc players. Bluray and HD DVD are not compatible so a disc of one type will not play on the other format. There are a handful of dual format disc players but they were expensive and few were sold. If you have HD DVD discs then you need to hand on to an HD DVD player if you want to watch them. All high definition discs on sale now are Bluray and of course will need a Bluray player to play them.
That is not possible since HD-players use HDMI for connecting to the television. It wouldn't be very useful to connect HD-players to SDTV's, because that way the player has no advantage over a standard DVD player.