New Laptop Hard Drive and DVD drive

Both my hard drive and dvd drive have recently stopped working so I purchased replacements. I assumed they would plug and play where I could install windows XP from the new DVD drive, but they computer doesnt recognize either.

“Primay hard disk drive not found
Fixed optical drive not found”

I have an A: promt from creating a startup disk, but I cannot do much else. If I try to change drives, I get
“Invalid drive specification.”

Any and all help would be appricated. How can I get it to see the new drives?

Thanks,
Jonathan C. Bagwell