The XtremeDSP Development Kit for Virtex-4 devices (http://www.xilinx.com/products/devkits/DO-DI-DSP-DK4-UNI-G.htm) is now obsolete,see the product page and XCN10031 for more details.
Windows 7 is officially supported by Xilinx tools since the 13.1 release of the ISE Design Suite (March 1, 2011).As the XtremeDSP Development Kit for Virtex-4 went into obsolescencesome time before Windows 7 support began, this kit would not have been tested with Windows 7 OS.
There is no guarantee that the XtremeDSP Development Kit for Virtex-4 will work without issues on the Windows 7 platform, and if issues occur, the recommendation would be to return to Windows XP.