I fixed a friends computer but failed to fix computer 2

[Steerpike]

The first one was easy. I walked in and almost burst out laughing. The wiring looked like a bowl of spaghetti. I unplugged everything cleaned it and rewired it all and presto! It worked and my friends were able to access the internet and everything.
The second computer is a 7 year old Dell with Windows 2000 on it. It would not turn on. So I opened it up and took it apart. I disconnected everything and cleaned it out (very dusty). I reconnected everything and it booted up. But, I received the error message where it says it needs a "boot disc" in drive c. I call the guy and he says he has no idea where his boot disc is...or his Windows 2000 disc is for that matter. I try installing windows xp, but I get an error message saying that it does not sense a hard drive (ide). So I take out his hard drive and connect it via usb to my computer and it works just fine. So I put it back in and now it won't even boot from the windows xp disc. I just keeps going to the error message (insert boot disc to drive c). I checked the bios and the bios does not seem to be sensing the hard drive either. I did change the boot order to begin with the cd player, and the boot order does include the hard drive. But, in the hard drive section (of bios), it says the primary hard drive is not installed. When I do the drop down menu to choose a hard drive to install, it does not include the HDs available.
It only has 512 megs of ram and 866 chip...it is old and feeble. I hate to tell the guy I can't fix it, so I will try to download a boot disc from the internets...I just need to find a floppy disc...do they still make them?

[canetoad]

1. Maybe the IDE cable

They get old and brittle.

[Steerpike]

2. Thank you

good idea...

[Duer 157099]

3. And if it's not the cable, it could be the connector on the mainboard

try connecting a different HD?

[Steerpike]

5. I don't have an IDE hdd

This is an old motherboard. I need to bust it open again and get the ID's for all the hardware.
They caled yesterday to tell me they bought another 2nd hand computer and it won't work either (garage sale)...maybe I can cobble the two into one working model. They just use it to surf the internets anyways.

[ChromeFoundry]

4. Does the BIOS recognize the drive

with the correct size? If the battery went dead, it may have just lost its settings.

on edit: oops, didn't read your post close enough....nevermind