Xp pro setup

Hello,
i have just takin my old pc out from under the stairs and need to get it back workin.i downloaded the boot cd coz i was getting a blue screen wit unmountable boot memory. thats gone now im at the repair and reinstall part of the cd and if i click the ~R~ key for rpair or enter to install i get this messege


setup did not find any hard disk drives installed in your computer.

make sure any hard disk drives are powered and properly connected to your computer and the disk related hardware config is correct this may involve running a manufacturer's diagnostics or setup program

thanks for all ur help and sorry if this was asked befor