Here's a quick rundown of the expansion slots found on motherboards ranging from the paleolithic era to modern day:
ISA/EISA: ancient slots back when PONG was considered high-tech and DOS 2.0 ruled the world.
VESA: When it became apparent that those 'speedy' 286/386 computers needed a video system boost, video accelerator cards would sit on this special dedicated slot while the remaining non-video cards (network, HD controllers) took up ISA slots.
PCI: As computer CPUs kept racing faster, the old ISA slots became a bottleneck. Motherboards of the 1st gen Pentium put all expansion cards (including video cards) on PCI slots.
AGP: Once again, CPUs got so fast, PCI video cards couldn't pass data fast enough through that PCI slot and we have the birth of AGP. A typical motherboard would have ONE AGP slot followed by PCI slots in the remaining spaces.
PCI Express (aka PCIx, PCIe): The newest current motherboards are likely to be completely populated with PCIx slots. For the current range of CPUs (Intel/AMD dual cores, quad cores) PCI Express should provide an overkill of datapaths to a videocard.
THAT TAKES CARE OF THE SLOTS YOU'LL FIND ON VARIOUS MOTHERBOARDS
As to videocards, it should be no surprise that MOST videocards in the stores today are created for AGP slots or PCIx slots. The two are NOT interchangeable. You must find out what your computer (motherboard) uses. Several ways to do this: Check the computer sales invoice to see if it's itemized, check WinXP's Device Manager, or in an act of desperation, yank out the existing videocard and bring it to the store with you.
While a computer CPU (Intel, AMD) does the heavy thinking, all videocards revolve around its GPU (graphics processing unit) to render a real-time 3D image and the two primary competitors are nVidia and ATI.
As others in this thread have indicated, it isn't necessary to break the bank and buy the newest/fastest/priciest videocard. A uber-pricey $5000hk videocard would be best paired up with a new dual-core or quad-core PC. In an ancient slow PC, a $5000 videocard would never reach its potential.
Your 2.5ghz PC isn't a slouch though, it just has a sloooooow videocard. For that kind of CPU speed, I'd recommend any videocard that's 1/3rd to 2/3rds the price of the top/fastest videocard on the market.
Your PC (with its relatively recent 2.5ghz CPU) can't be SO OLD that it
only has PCI slots. If you're absolutely positive on this, then your quest will be to find a fast videocard made for the old PCI slot. I don't see much success there, ATI/nVidia stopped making PCI videocards by now.
More likely, your MX440 videocard sits on a dedicated AGP slot. Go visit your motherboard. If the MX440 sits on a brown slot, it's AGP. If it's sitting on a white slot that looks like ALL the other white expansion slots, it's PCI.
I don't know what PCI Express slots are colored, but am pretty sure they laid the MX440 GPU to rest long before PCI Express was introduced by motherboard manufacturers.
That takes care of how all this stuff physically relates to each other.
For GPU comparisons, peek through review sites like
AnandTech,
Toms Hardware,
HotHardware, etc
Find a videocard whose drivers at least support DirectX 9.0 or higher, Shader 2.0 or higher, and preferably at least 256megs of memory.
