Doom 3 faulty

I know this is a common error, but I have yet to find any sources that solve the problem.

I recently installed Doom 3 for my machine, but every time I attempt to start the program, a window pops up prompting me to insert the first disc

The prompt is something like this -
*please insert disk 1, click OK and restart application*

It continues to ask this, even though the correct CD is already in the drive. It isn't mislabelled because I already used the CD to install the software.

I downloaded a bunch of cracks, including the "NO CD" crack but it still doesn't work. Can anyone help me as to why this isn't working?

 

have you tried using the 2nd cd?

 

Yes, it still gave me the same prompt.

 

where dya get your copy from?