Look for the mfr website for support.
I have the Bytecc model (rebranded Silicon Image) it works for both Vista and Win7 despite not mentioning them on the mfr site.
I also had the Vantec model, but never tried it with Win7, just Vista 32 & 64.
Usually Vista drivers will work, but aren't guaranteed.
BTW, here's the SI driver page for the 3132 controller that is the underlying component of my Bytecc one and the Win7 64 bit is 1/5 of the way down;http://www.siliconimage.com/support/searchresults.aspx?pid=32&cat=3