pooch - You asked about the Rosewill - it does exactly what the SIIG card does - sometimes Win 7 detects it at boot when it's already inserted and sometimes not.
As for running the XP driver in compatibility mode, I'm not sure how to do that. The VIA and TI Firewire drivers are built into Windows - 7 and XP - so there's not an executable installation file to run in compatibility mode. Also, I don't know for sure where to get the XP drivers. Just copy from Windows\System32 from an XP machine? If you know a way to force the drivers to compatibility mode, I'll try that first. If not, I'll look into the USB procedure you mentioned. You say that the drivers must be uninstalled, but since they're MS/Windows drivers they don't show up in Remove Programs.