I know this is a little late on the scene but here's a direct link to the drivers from the SteelSeries downloads page for Windows 7 64 bit drivers;
http://downloads.steelseriescdn.com/drivers/keyboards/zengine/ZE_25030_NA_64.exe
If you need 32 bit drivers they are here;
http://downloads.steelseriescdn.com/drivers/keyboards/zengine/ZE_25030_NA_32.exe
These drivers are directly from their downloads page under the Z-Engine for Merc, Merc Stealth, Zboard, and Fang section on the bottom right-hand side of the page.
Once you have them archive them to a thumb drive or even a CDROM to make sure you have them again should you ever need to reload.