Can a Blue Ray player also play a regular DVD? I have a collection of "old" DVDs that I don't want to sell yet and would like to still be able to watch them without having to switch back and forth between the new blue ray player and old dvd player.
Yes. Go for it! You will be pleased with both (similar) results, especially in certain scenes of Blu DVDs where they genuinely take full advantage of the technology. This reply assumes your TV is HD capable and its' scan rate (refresh) is a minimum of 120 mHz.
Buying a Blu-Ray machine with the intention of feeding it to an old CRT TV set makes no sense, unless the next update to your home system will be as mentioned above.
Yes, DVDs still play on Blu-ray players, as well as Compact Discs (Music CD). I have also found that some of the cheaper Blu-ray and DVD players (Magnavox, Coby, etc.) will also play video CDs (VCD) and just about any type of disc I throw at them, while the more expensive players (Sony, Samsung, etc.) are very finicky about what they can play back.
Blu-ray players also "upconvert" your DVD to HD, and make your old DVDs look better. Not true HD, mind you, but they do look better.
Actually I bought a blu-ray this holiday season. My plan was to use it with a new TV for the bedroom that would be about 22" but I haven't found one I like at the price I want to pay, so now I have the DVD without the TV. LOL It's just a basic player though so I don't know that I want to attach it to my main TV since that DVD has much more going for it in terms of functions.
Yes, a blu-ray player can play DVD's. You may really want to upgrade your television set, if you haven't already. The picture won't be worth it on an older tv and you may have great difficulty hooking it up, if at all.