I have a similiar issue the 'Dell' page of my 8500, except I'm on win 7, and, unlike the OP, while I cannot always see the Dell logo (and sometimes i do see it - have no idea why), i'm always able to enter the bios by quickly pressing the f2 button about 1 second after power on.
In either case - Dell logo or not - I find you have to be extremely fast to get into the BIOS.