I have a very specific problem - Can you help?

I bought Sims2 for my 9 year old son, Rory - and he is desparate to use it.

I have loaded it (tiwce) but cant get it to run.

With disk 1 (of 4) in the CD rom drive, I get an error message (insert cd rom and try again) but it doesnt work ..

Have you come across this before ?

Best regards

Allan