Colored Dots & Monitor Flashes On and Off Help

[Kaleb1240]

When My computer Starts up some of the technical letters of the words are colored or capitalized where they shouldn't be, after this the Microsoft logo and progress bar loads, there are little colored dots ALL over the screen. When I get to the start up page i used to log into my user and it would either take a long time to load, or freeze up. When it did load however, i could use it for about 30 min. then the monitor would start turning on and off but the power light stayed on. I still have little dots all over the desktop. I didn't want to bother with it so i left it alone for 3 months then i tried to turn it on the other day and right after i logged into my user i had a blue screen. I have gotten a blue screen before and it would say I had a driver problem but this time it didn't list any problems with the drivers. I'm not very technical and could really use some help.