I had the same problem on Presario SR 1750 NX in which the CD/DVD ROM all of a sudden quit recognizing the presence of media in the drive. I had successfully upgraded to Windows Vista 6 months ago and successfully used the DVD drive for the six months.
Last week it quit working and said "please insert media" even though a compatible CD was in the drive. I have had this happen previously on other machines and was able to get CD Creator and Nero read and write some of the time.
I downloaded the Nero trial and the copy function was able to see and read the media in the drive. No other application worked. So it had to be a software problem. Unfortunately HP support stinks and they don't have upgrades shown for Vista.
I have since added a second drive (Sony) which works fine, but I would like to get the original drive working.
PS. On another Presario SR1750 NX problem, I was all set to add a second SATA hard drive and there was the power connection and bay for it, but I could not find a place on the motherboard to connect the second "red" SATA connection. Does anyone know where it connects?
PS.PS. On another note, in contrast to HP, Microsoft spent three hours on the telephone with me helping me successfully upgrade to Vista Ultimate.