Could be driver problems, that arn't used by Safe mode. Like graphics, network or CD support.
In safe mode check that you have no "?" in device manager, and that the above drivers have no problems. perhaps reinstall graphichs drivers as a begining.
Device manager can be found in SYSTEM in control pannel under the Hardware tab. You should uninstall graphics drivers in Safe mode and try and boot normally, this should revert to default and 640x480. if it works you can install new ones.
If this fails, do Anti-Virus and Spyware checks. Could be corrupt system files, in which case Windows Repair could help, but, its not far off a rebuild in that situation, with files backed up from safe mode.
Have you installed any new hardware that caused this to happen, or did you just turn it on one day, and it wasn't working. Have you left it a good half hour hanging just to check it eventually doesn't give any errors.
Before your repair or rebuild, In safe mode, go to Event Viewer in admin tools, and post any system error or warning messages that have recently occured. google them as well, as common faults are easy to find, and is what most people here would do to help anyway, and anything proactive is always going to make people want to jump in and fill any blanks.