My samsung VM8000 keep coming on and off and cant detect the hard drive?

I switched off my computer and after sometime switched it back on, but it wont go past detecting the hard drive. It just keep switching on and off, sometimes it doesn't even detect the hard drive. it wont even go past the first screen when you switch it on, whats wrong with it? this happened after I had AVG 8.5 running on my system for 3 weeks and then Kaboom! this happened. Does anyone have an answer please.