yeah, so boinc is seeing the gtx295 cores. you need to put in a script to use the other 2 gpus.
Create a cc_config.xml file in notepad. The contents should be
The 1 = true, 0=false in the statement above. It does not mean the number of GPUs you have
Place that file in your BOINC data folder. In windows XP
"C:\\Documents and Settings\\All Users\\Application Data\\BOINC"
in windows 7 it will be in the "c:\\program data\\boinc" folder