server 2008 SP2 will not install

Hi All,

I have an Acer G540 running SBS2008 and exchange.

My problem is that after installing all available updates I am unable to install server 2008 SP2.When I try I either get an error 800b0100 or the install tells me I have to install SP1 to continue even though SP1 is installed and has been for some months.

I have applied the MS fix for the error but still get the message regarding SP1 not being installed. I have even tried the standalone updater as per MS but still the issue remains.

Any help you could provide on this would be very much appreciated.

Thanks.