From the list of available drivers, there are Windows Vista Drivers for this board, which means this board does support Windows Vista.
It supports both the Vista 32 bit and 64 bit and many more other operating system as you can see from this link: http://downloadcenter.intel.com/Product_Filter.aspx?ProductID=2068
Also from this link: http://support.intel.com/support/motherboards/desktop/sb/CS-008326.htm
Hope this will be helpful.
Memory support for this board can be found on this link: http://support.intel.com/support/motherboards/desktop/d945gnt/sb/CS-026631.htm
In short, this board supports a maximum of 4GB.
Hope this will answer your question.