weird xp prob

ok heres the prob sometimes my win xp sp1 acts up it will show an icon on my desktop highlited as if my pointer was on it but its not and if i run up ie the page scrolls down and wont let me scroll up this started happening shortly after changing my g-force card to a readon 9000. but over a years time i replaced my motherboard,ram,amd processer,hd,network card and video card to a readon 9600.i updated the bios i reformatted and it would do it befor i installed any drivers or programs. i went through the bios settings changing some of them nothing has worked.i,m almost to the point of chucking this thing and saying to heck with computers lol any suggestions would be apreciated