Have owned an HP Pavilion Elite 210f for several years. I set it up for dual boot into Linux or Windows, and had only one problem until now. 9 months after I first bought it, the hard drive went bad. Took longer and longer to access data, saw tons of read errors in the logs. Found an issue with the hard drive too aggressively powering down to save energy and applied an update to its firmware, but it didn't help. I replaced it with another Western Digital, WD1502FAEX-0, and had several years of trouble free use.
Now the computer is acting weird during a cold boot, after the machine has been off for a while. It takes the BIOS longer than usual to detect USB and hard drive. Sometimes it hangs at this point. Most of the time, GRUB (version 2) comes up and puts the boot menu on the screen. Then sometimes the keyboard does not respond, not even with the num lock light when num lock is pressed, so maybe that means the USB wasn't detected after all? When the keyboard is working I see another problem: GRUB is supposed to count off the seconds before booting the default OS, but this countdown is sometimes absent. If a key is pressed, GRUB is supposed to stop the countdown, and I've read the hardware can insert a keypress in the buffer if it's behaving badly. If I continue booting, the boot fails with the Linux kernel complaining it couldn't find a root drive and dropping to the (initramfs) shell.
If I leave the computer powered up and wait 5 or 10 minutes, or more before trying to boot, it all seems to work fine.
I've run memtest and found nothing wrong. Also ran a hard drive test with WD's dlgdiag5.exe program. Nothing wrong there either. Only bit of hardware I've added is a small webcam that plugs into a USB port and the microphone input. Other than that and the replacement hard drive, there is no change in the hardware from original. I've tried blowing out the dust and reseating the RAM. The cleaning didn't have any effect as far as I saw.
Do computers still use a watch battery for the CMOS memory, and could a bad battery cause this? A problem with that idea is that the computer is not forgetting the time and date.
I've also checked for firmware updates, and there aren't any that are applicable to mine. There's more than one kind of Pavilion Elite 210. Mine is the one with an AMD Phenom II and a Radeon 5400.