computer has goback internal error

hi, my dell dimension 4600 will not boot up. when i turn it on it brings up the sytem works logo and rectangular info box that says press space bar to fix problem. that stays on the screen or about 5 min then the screen turns black with a goback internal error also showing a                                 failure code gb_genlog(181). any ideas. ive tried to us the recovery disk and does nothing and also used symantecs cd to fix and has not worked. everybody keeps telling me to push f8 while booting up but thats is not an option that works on my computer only f2and f12????????????