|If you're getting the 'primary hdd 0 not found' then you're not booting from that drive. Maybe you're restarting it several times until you don't get the error and then it boots? Otherwise as modify.hardware implies, it's booting from another drive or the drive's cabling or jumpers are set wrong.|
But even if that's the case, if the drive is good it will boot up OK.
Can you remove the drive and attach it as a slave in another computer? That way you can copy off any data files. But you can't copy off installed software and have it work on another drive. When software is installed it puts a lot of files in different places and makes changes to the registry. There's no practical way to do that manually.