If its a replacement for the original then you probably need to check you jumpers. Or maybe you forgot to plug in the power/datacable.
if you put in a second hhd, sometimes the system will want make the new drive the main boot drive. So you need to go to bios and tell it to boot from the old drive.
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Ive got the same problem. You press f1 and it goes to the desktop and boots the software and everythhing seems ok. It just wont be found at bootup. The bios shows the hard drive. Ive tried a new cable, moving it to the secondary spot and changing the jumper from the default setting to the master duel setting. Nothing seems to work...