The problem is the driver for Firewire in Win 7, I think. This has been discussed many times in this forum, use the Search function for "Firewire". I got 17 answers.
The problem seems to be with Windows 7 drivers, although Windows 7 installs the Firewire card, it does recognise my player or camcorder, I have tried all the drivers I can find, including the Legacy driver, but nothing seems to work, any other ideas anyone?
I think you're right, the standard Win 7 Firewire driver seems to work with virtually no Firewire devices!
However, I'm very surprised to read that you've tried "all the drivers you can find, including the Legacy ..." I'm not sure what all these drivers are but, for me, at least the Legacy one is the requirement. Are you sure you have correctly installed the Legacy driver? What does Device Manager show for "IEEE1394 Bus Host Controllers"? I've attached here what it shows on my machine. As you can see it shows two controllers (I have several FW ports), both with the Legacy driver.
As a result all my Firewire devices are correctly seen by Windows and fully operational.
Re your latest comment: I have Win 7 and a Firewire PCI card (as well as on-Mobo firewire). I've never had problems importing DV via Firewire (once the Legacy driver was installed.)