Desktop w/xp (ddr) and firefox. Need help narrowing down my pc prob . when i plug in cd rom? wont boot up. unplug cd? boots up fine! bios says "no hard DRIVE detected". It is not cd rom as ive tried several verified functional cd roms. tried all possible component connection plug in variations. replaced all wire leads. replaced power supply. So i think ive narrowed prob down to hard drive or motherboard yes?  :-\Can anyone out their help me pin point this problem?

PS all said components were functional together at one time. tho its been a while, cant remember exactly why i unplugged cd and floppy. think i changed towers or power supply or something like that Check you jumper settings. Not clear what you mean.
With NO CD-Drive present, the system is normal. Is that true?

Are both Hard Drive and CD-Drive the standard PATA type?
Or are either or both SATA, serial ATA devices.
This is an important detail

Is this a new computer? HOMEMADE?
Was it alright a few weeks ago?
Have you had any other recent problems

Best grues, from what information you have given,is the mother board is at the end of its useful life. Does the motherboard support SATA?

Answer to first question is Yes, With no cd rom present? system boots up normal.

Computer is homemade but fairly new.
Muthaboard-('06 ECS mdl#P4M800Pro-M)Intel pentium4  supports SATA LAN & DDR/DD2 w/700 mg of RAM

HD-('08 Maxtor 80G) and supports PATA

CD-('98 sony)  label says ATAPI

Power Supply-('08ArrowMax 450W)

OH! now i sorta remember what happened. Computer was working fine, including cd rom This I'm sure of as I played Tiger Woods and also installed some hardware using manufactures disk.
          It was time to PERFORM routine maintenance. So I disconnected power leads and thoroughly cleaned unit using compressed air.
           After said cleaning I couldn't get machine to boot up. It was a nightmare. But after several days of trying everything humanly possible. I eventually got working by simply removing and replacing RAM sticks. Problem solved!. Booted up, everything worked fine. BUT! At that time I only had HD hooked up. No cd rom or floppy present. Well I was so happy to have my pc back and to afraid of messing something up again. I just left cd disconnected. Until a month ago when I needed cd rom but couldn't get to work. That brings us to this point.

Note: tried changing jumper configuration                       






 Are you using a single cable to connect both HD and CD?
If yes, try swapping the connectors around. i.e. the one currently connected to the HD, connect it to the CD, and connect the other one to the HD.
NOTE: It is BETTER to use separate cables (controllers) to connect HDs and CDs.
Replace the IDE cables with brand new ones.