This may be a little more help
https://www.centos.org/docs/5/html/I...all-bootloader
If you choose to there are mount commands that can be mounted from debian to be able to just run update-grub, but assuming that if update-grub doesn't see your lvm's now you may just want centos to control grub.

If you have Gnome, or MATE, installed you can install gnome-disk-utility and use that to see what is available for mounting and use it to mount them.

I re-installed CentOS 7 and everything is ok now.

EDDY1 & k3lt01:

I have a brand new 1 TB drive that the manufacturer sent me because the 500 HDD in my desktop went south (bad sectors) I can open the case, install the new drive and boom I've got the whole drive to install Debian on.

This way Debian will have it's own drive and the other 500 GB HDD drive has Slackware installed on it.

I'm not sure entirely sure how LILO and Grub would work together but I'm thinking that the 500 GB HDD will be dev/sda1 and the 1 TB drive will be dev/sdb and both should show in the bootloader.

Would Grub take over LILO?

I don't know, I assume Grub would see sda and then boot Slackware without using LiLo.

Guess I'll find out after I install it--

I have to purchase the cable that connects from the 1 TB drive to the power supply and I think I also need a sata cable that goes from the drive to the mobo.

I'm so glad that I can install Debian to the 1 TB drive. I really like it.

Or you can elect not to install grub & edit lilo

another option is to install grub to sdb and make a chainload entry in lilo.

If I understand you correctly during the Expert Mod Debian installation don't choose a bootloader and when done; I should be able to edit LILO?

I'll look into how to edit LILO, as I haven't before:-

I'm not familuar with making a chainload entry in LILO but I will look it up; thanks; colorpurple.

I found an extra pci-e 8 pin cable in my old desktop tower box.
What I don't have is the SATA plug: this one:
http://www.microcenter.com/product/3..._SATA_Cable_36

If I'm not mistaken (haven't opened the case yet) the PCI-e cable that's already serving the 500 GB HDD should have additional plugs that plug into the HDD.

If I reading this right you're talking about the power cord. Even if you don't have an extra sata power cable, some power supplies still provide the 5 pin cord that you can buy the sat converter to connect sata hdd.

I misread the last question you may have the port but usually there are no extra cables unless you built it yourself. Or removed a sata drive.

For some reason when I installed the new 550 watt power supply it came with 2 extra cables.
I'll pick up a sata cable as soon as I can.

I did remove an old HDD in the past that had bad sectors and replaced it with a new 500 GB Toshiba HDD.

I'm looking forward to running Debian Jessie on my desktop-

If the power supply is modular the cables are not attached to the supply until you attach them.
If the power supply is not modular some manufacturers also supply adaptor cables (e.g. molex to sata) so you can use different hardware configurations.