My computer screen only has a blinking line at top.

When logging onto my computer I can see the load up screen and then it goes to a black screen with a blinking cursor at top left. Before this happened I was trying to download the upgrade of AVG.  I downloaded the file but was not able to install it when I tried. Then I got a CD in and tryed to install it from that and it said it was a older version. I didn't try to install it and then tried later and it said it was a bad disk. I've also been getting messages like my computer keyboard is bad and the keyboard was beeping when I pressed any key then yesterday it worked. I was able to get logged in and to the point of trying to dial out once yesterday. When I dialed out it said it was not able to access the server. When I shut it down I had the black screen again. Any ideas? Thanks.