Try:
http://www.gameboy-advance.net/You may need these newer (Visoly?) files: XtremeLink.zip, Xtreme_USB_v20712.zip
If you can't find them, PM me your address and I'll send them on disk on the mail.
I have the 256mb version of your card and I had a beotch of a time getting it to be recognised and thranfer roms to the cart. I had to install, uninstall and re-install several times before I got it to work. Plus mine came with a device so I don't transfer using the gba, just the flash card reader type thingie. BTW my PC has USB 1, I think so that shouldn't be an issue except maybe for rom transfer speeds.
LMK how it works out for you, Ron H.