unable to play DVDs with Real Player

I have a Compaq nx9030 laptop. It has a Toshiba DVD-ROM SD-R2512. It came with Intervideo WinDVD 5 player. I used to be able to play DVDs- not only on WinDVD, but also with Real Player and Windows Media Player. My preference was Real Player since I didn't like the winDVD controls. Something has recently gone wrong where I can no longer play DVDs with Real Player or Media Player. WinDVD still works like it should, but trying to view DVDs with Real Player or Media Player always results in a "key exchange DVD copy protection failed" error. I reinstalled the latest version of winDVD off the HP/Compaq site, and reinstalled Real Player. Still the same problem. The same DVDs play fine on my other Sony Vaio laptop with Real Player and Media Player, and used to play fine on my nx9030. The Vaio also has Intervideo winDVD 5. Any ideas on this? Driving me nuts.

 

Problem solved- ran dvdupgrd /detect command and discovered I had somehow installed an elecard decoder when it should have been the IVIDIDEO.ax decoder. Unregistered elecard mpgdec.ax and was back to normal. Thanks anyway.