just had an extra ahrdrive installed, but i have lost my other drives please help

is the extra hard drive on another IDE cable?

how many CD/DVD drives have you got?

both harddrives are connected to the same ide lead.
i have 1 cdwr drive and 1 dvd rw drive

are the CD and DVd drive connected to the same iDE cable and is this connected correcrly into the motherboard?

are the drives set as master and slave?

are the drives showing up in the BIOS?

yes they are both on same ide. a friend did it and hes normally reliable so yes i think they are in the correct place.
how can i find out if slave or master
and bios sorry dont have a clue

What error message are you getting that leads you to believe you have lost your drive? Or does it not show up in bios. State your model # of computer at least so we can tell you how to access bios. The more info you give the more easier it is to trouble shoot your problem.