First off, I will never let a laptop run when I am sleeping. It makes no sense. These are laptops that I own outright and bought them new from Dell. I've also got relatives and friends that have never had problems with Dell laptops and some of them have left them on for weeks at a time without problems.
I repair lots of Dell, Compaq, HP, Gateway, Acer, etc., and rarely do I ever have to replace mb's or cd/dvd-roms with Dell. However, I've replaced lots of mb's with HP & Compaq. All manufacturers have problems with hard drives. I am not particularly fond of Seagate/Maxtor hard drives. I've had problems where they would not honor warranties. I've had lots better performance, efficiency, and longevity using Western Digital.
I personally recommend Dell. If someone ever gave me a Compaq or an HP for my own, I'd use it as a boat anchor. To me, they're junk! I've had tons of problems with Compaq/HP. All manufacturers lie but Compaq/HP lies the most. They're almost as bad as Microsoft or better yet...politicians!