I have a Dell Latitude D830 that constantly re-boots. Have tried countless remedies, any suggestions please? Pulling my hair out! Thanks, Danny.
I guess you tried to clean or reinstall your OS. If you already did...
It may be related to a heating problem, try to monitor temperatures with speedfan to see if it goes higher than 90°C. In this case you should try a laptop cooler or you could clean the dust off fans and heatsinks. If you want to disassemble your DELL to remove the dust, read the official service manual.
Else, if you got a bsod like Journeyman Geek suggested, chances are ram is to blame. Check your ram with memtest then replace the faulty ram stick. If its not the ram, could be the hard drive, check the S.M.A.R.T health test of the drive.