thanks Matthew. so if i were to get an HD 5970 what kind of mobo should i get?
Any board with a PCI-e slot will run any video card on a PCI-e format, which is what a 5970 is on.
If you had a card with AGP slots, you could only use AGP cards in those slots, PCI slots, only use PCI cards etc.
And motherbaords have many different things about them:
To generalise for the "mainstream" computers, some are Intel, some are AMD, there are different sockets for those, for instance, the current AMD boards are either AM2+, which run AM2 and AM3 CPU's, but only have DDR2 memory support, and AM3, which supports all AM3 processors and uses DDR3 memory.
The type of memory differs, different speeds can be used on different boards, and differen tboards support different amounts. There are intel boards that support dual channel (memory in pairs) and some that support triple channel (memory in threes)
All modern boards now will come with PCI slots, which are for expansion cards like sound cards, NIC's, RAID controllers etc. Most also have PCI-e slots (what your 5970 takes) and these are for graphics cards. Some have more than one PCI-e slot, so can have more than one graphics card in. For ATi cards, it is called crossfire, for nvidia, it is called SLI. So long as your board has the right slot, it will run any card on that slot (but just about all modern graphics cards will require external power from the PSU aswell as power from the board).
Motherboards have different number of slots on them too for things like internal USB (different to the USB on the outside that your mouse, keyboard, camera, memory stick etc plug into), SATA slots (for hard drives, DVD drives etc) and IDE slots (getting redundant now, but was the main platfor for Hard drives and CD/DVD drives).
Some boards have different features on the back panel, such as integrated graphics, integrated sound, different numbers of USB slots, firewire slots, eSATA slots etc.
There are differences with the main chips on them too, the northbridge and southbridge (I won't go into details about them, google it and look it up). Some go at different speeds, some have features that otehrs don't, like the infamous ACC on AMD boards that lets you unlock the 4th core on Tri and dual core AMD processors.
Tehre are many manufacturers for them, but the best known would be Asus, Gigabyte, MSI, Foxconn, EVGA, ASrock and Biostar. Some have larger ranges and are higher quality than others and have different featurs that you can't tell without using them. For example, Asus boards have Asus EZFlash, which makes it easier to Flash (update) the bios
4500