Thank you so much for your help! But our cases might

be different. My problem is that pc doesn't recognize my Chinese installation CDs, while these CDs had successfully installed Chinese OS before on my pc bought in China.

I googled multiple-operating system on line and did found similar problems, eg. pc bought in Japan can't install English OS or Chinese OS. However, no solution was found.

Anyway, thank you very much for your kind help and have a good evening!