I have a IBM Aptiva 2170 and going to upgrade it later on. What is the big black long port just below my 3 PCI ports? Here is a link to what I can find of it.
http://media.photobucket.com/image/IBM% ... c85b64.jpg

I'm wanting to buy a new motherboard off online and install it in my Aptiva and try to connect/combine it to the Aptiva board, So that way it has its orginal board and a new board with it. Everything in my Aptiva is orginal. 64MB RAM 10GB Hard Drive, basic CD-ROM Drive accept for the upgraded to Windows XP from Windows 98.

Older Motherboards had an ISA slot. That black slot looks like one. You might be hard pressed to find an ISA card these days. It's an obsolete slower interface.
http://www.arstech.com/ccp51/media/imag ... -step1.jpg

whay does a ISA slot do? Is it a older PCI slot?

Yes, but much slower...ISA is16 bit addressing, vs. PCI at 32 or 64bit.

http://commons.wikimedia.org/wiki/Category:ISA_cards

What is your budget for upgrading?

Considering the age of your system, you'd most likely have to drop everything (CPU/mobo/ram/hdd/video card/PSU), gut the machine and just drop everything in. You can drop some serious cash on this or actually get a very powerful system for a cost that won't really hurt your wallet.

You don't want ISA. Its been dead for years. So is AGP. PCI is dying out too. As long as you have a motherboard with pic and pci express, you're set.

Actually, after re-reading your post, what exactly do you want? Your motherboard is dead? I'm a little confused.