lost my cd rom from my pc

I nstalled widows xp. then my 2 cd rom showing on my computer. Tthen after I installed Nvidia for my vga card and I reboot my computer my 2 cd rom disappeard. then I went to regedit and removed low filter from glass and came one cd rom..I still missing the other one. I need help to retreive the other cd rom..thanks.

Mike