I am trying to install my old AST hard disk into my 1999 Compaq as a secondary hard disk. I plugged it into the same cable my CD is using. When I boot up, the CD nor AST hard disk show up. Is this impossible to do?

It sounds like you forgot to change the jumpers. If you have 2 devices on the same IDE channel set to master, they won't be recognized right.

Try changing the jumpers on the CD to slave, rather than master. Then enter your BIOS setup & make sure that the master & slave are both set to AUTO(detect). Save changes & exit Setup.

HTH

Dave

and place the hard drive on the end of the cable as Master with the CD in the middle of the cable as slave.

you may want to check to see if the jumper on the cd is set to CS (cable select). I see alot of compaq and hp use this cable select setup instead of master/slave setup.

How to Prevent Drive Letters from Changing After You Add a Hard Disk or a CD-ROM (Q282530)
The information in this article applies to:
Microsoft Windows Millennium Edition
Microsoft Windows 98 Second Edition
Microsoft Windows 98
Microsoft Windows 95
http://support.microsoft.com/default.aspx?scid=kb;EN-US;q282530