Keyboard text jumps around and writes backwards

I run Win XP Pro and recently got infected with 4 trojan horse virus. I had to complety format my HD and re-install windows, but the problem Im having now is keyboarding text. Here is whats happening. I can type a few words of text fine... and then what happens is the text jumps up to the middle of the first line of text and inserts what Im writing at that point, or it will allow me to write 5 lines of text and then jumps up to the beginning of the sentence and inserts what Im typing at that point. I cant rename folders either...it jumps out of the typing scheme into my workdesk at which point, I have to click back into the folder and try to rename it again. Very strange! It has even written. backwards ( righ to left) as Ive typed a sentence. Its very annoying to say the least. Ive reloaded all the the drivers that came with the computer, so I know they are correct. Even writting this now, its jumping all over the place. Ive scanned and there are no more virus showing. Help!!!