Dell inspiron 1545 not turning on

Hello,



virtually new laptop running windows 7

when press power button, laptop boots on fans whiz round white power button stays lit, has power going to laptop as i can open dvdrom drive - but get nothing on screen

have stripped out the battery, swapped memory, removed hard drive, held power button down - even been as far as checking board for spillages, checked power socket, connected to external monitor - still nothing

but if i hold the "FN" when powering up i get - 7 short beeps followed by 2 fast 1 short beep then 3 short beeps constantly

if some one out there has any help would be grateful