The W3622 cannot handle a dual core processor, at least not a Wolfdale. I know from first-hand experience.
The W3622 CAN handle any video card you throw at it that goes in the PCI-express x16 slot (pretty much every video card out right now).
Yes, just make sure its a pci express video card.
More information: The master computer is an Emachines computer model number W3622 The current master hard drive is model number ST380815A5 The computer I am extrating this hard drive from is a Compaq Presario Prod#PW791AA The soon to be slave drive is model number ST340015A ------ I need novice directions on how to add this to my computer starting from scratch. I have the soon to be slave hard drive removed from the Compaq, but I need to know how to put it into the Emachines computer and make it the slave drive. You can also contact me on AIM. My screen name is ThePrepH8er1990.