Depending on the exact model of 2420, it comes with several different cpu's. Latest offered was a second generation Intel core i3-2348M processor. System specs?
Looks recent, is it under warranty?
Test: Start BIOS/UEFI by turning on system and enter the magic key (F2?) while manufacturer screen is still displaying and check for HDD being seen and present there. 'No bootable device found' is a standard message when either the boot sector on the HDD is corrupted or is the result of a HDD crash/failure.
If you see the HDD in BIOS/UEFI then it is running. If not, then it is likely gone.
Recover all important files using a LIVE CD of LinuxMint here if HDD is live and running: (32-bit or 64-bit) http://www.linuxmint.com/edition.php?id=105 or http://www.linuxmint.com/edition.php?id=106
Burn the .iso file using native burning program in Win 7 or 8 to blank DVD. Google instructions on how to run a LIVE CD (no install needed) to recover your files.
Finally Got It All Apart Just To Find Hard Drive Is Secure And In Place Correctly!! But I Removed It And Re Installed It Just To Find The Same Start Up Message No! Bootable Device Found?? Is The Hard Drive Toast? Or Is Something Else Wrong? Also After Re Seating It I Held It Together To Restart Same Message But When I Felt The H/D It Was Really HOT!! Thanks Tom