Help!

I have a dell L400 L/top which has prooved ideal fro travelling because of it's compactness. $ moths ago i fitted a new H/drive and did a clean xp load it has worked fine. I haven't used it for the last month on turning it on all i get now is the dell logo and the press f2 for setup etc. it then stops I cant enter the bios or anything. It's not getting to use the h/drive and I've tried different memory any clues? All I can think of is the bios has got stuffed.