My computer freezes on desktop.

Hello,

Im having alot of problems. my probles are the computer will start up but when it gets to the desktop it loads up avast anti virus and then it will freez there it wont show my internet is conected or anything. the only way i can get back on is going onto safe mode and back up like 5-60 minuts ago. but when i do that my computer starts up and runs just fine. its just when i restart when it gets to descktop it freezes and if i click on the windows key the bottom bar turns white and just loads but the red ligh on my computer doesent even blink. i cant even do ctrl,alt,delete it just sites there i wanted to see how long befor it lodes i left it there for 5 hours and it dident even load. a couple weeks a go it told me that it couldent find my hard drive wile i was in windows but the computer still ran just fine. what should i do.