I am sorry to hear that have had issues with your motherboard model D975XBX2.
Please bear in mind your motherboard model was not designed for your operating system version.
See details of supported operating systems here:
In addition to that, I would recommend checking with Microsoft if you are looking for different driver versions.
I understand, that this thread is ancient and likely no longer of any relevance to jstateson.
For reference though (and for future users finding this via a search engine, like me), here is the latest Marvell 88SE61xx driver, served directly from my home server:
Marvell 126.96.36.19900 Windows driver for x86 and x64 architectures (Supports 88SE6111, 88SE6121, 88SE6122)
If you do not trust me as a source (which would be understandable) or if my server ever disappears from the web, please just search the web for the version 188.8.131.5200, you should be able to find several sources, at least as of now. Note that I have not tested these under Windows 8.1, but to my knowledge they're the latest you can find. This driver has been released by Marvell on May 23rd/24th 2012 according to mv61xx.inf and the file time stamps. A shame that Marvell only releases to manufacturers/OEMs and not publicly.