Inspiron 8000

So ok I got an old Inspiron 8000 with a new hard drive and operating system. All the drivers and everything have been installed. It was running great and then one day I come home to find the screen frozen. I reboot and have some trouble getting the system up and running. When I finally do, it is working fine and then suddenly freezes again. I get an error message saying something about a kernel and a physical memory dump. After that, every time I try to reboot it I get a message that says no bootable devices detected press F1 to reboot and F2 for systems options. HELP!!