|See if you can get into your BIOS set up screen (typically press repeatedly a specific key during start up - maybe F1, F2 or Delete, but can be others depending upon mfg or MB mfg). Since this does not require the access to your hard drive or windows, it may tell you a lot about the problem. If you cannot access your BIOS (you should if you got to the safe mode beginning at least) then you definitely have a hardware issue (you still might). If you have access to your BIOS, set it so that it does not automatically restart upon errors, save changes, and restart. This should show you what the error is and you can copy it down and post it here for others to help you with (or google it yourself to see what it might be related to).|
Note: a common hardware problem is a failing memory module, to test this possibility you can boot from a disc you prepare with Memtest on it, or if you have two or more memory cards, you can try starting with first one then the other installed individually. If it starts with one, replace the other one.
You have to be a little bit crazy to keep you from going insane.
If all else fails, read instructions.