Help with dell and hp!

i've got an hp that i'm having a lot of trouble with. when i turn it on i get taken to a black screen that gives me the option to start windows normally. when i choose that option i am then taken to a blue screen that runs me through a bunch of stuff but the only way to get off of that page is to do a hard shut down. none of the f1 f2 f3 etc keys seem to be working and i need to know how to get to the boot menu. and also does a dell os work on an hp?