Windows Server 2008 x64 R2 installs and seems to work fine on the SS4200.

One of the major issues is that a driver for the SIL3132 is not available for 2008 x64 R2.

I was able to get it running with the following procedure:

I downloaded driver version 1.0.15.6 from siliconimage.com under the drivers listed for the SIL3132.  It is listed as the base driver for windows 7 x64

unpack the driver zip file and under AMD64 SI3132.inf was modified in the following way:

%PCI\VEN_1095&DEV_3132.DeviceDesc%=SI_3132_XP, PCI\VEN_1095&DEV_3132&SUBSYS_31328086

was added to the bottom of section: [SI_HDC.NTamd64]

HKR,SupportedSubsystemIDs, %SI3132_SUB_ID_DESC_INTEL%, 0x00010001, 0x31328086

was added to the bottom of section: [SupportedSubSystemIds_AddReg]

SI3132_SUB_ID_DESC_INTEL="Silicon Image SiI 3132 SATALink Controller (Intel)"

was added to section [Strings] right underneath the line: SI3132_SUB_ID_DESC_DELL_3="Silicon Image SiI 3132 SATALink Controller (Dell_3)"

Finally, go to the mass storage controller with the yellow warning mark, select update driver and navigate to the AMD64 directory.

The driver should be auto detected.  You will get a warning that the driver is unsigned.