Firstly im sorry if this has been answered before in oither threads but im not very good with computers and have no idea of the terminology.
I have a compaq f500 presario using vista as the OS and pretty much every day if its been left alone or on for few hours it crashes all the icons and any open windows all move to the bottom left corner of the screen and the tool bar goes a solid grey colour so i cant open anything from it. Also when i try and open the start menu it pops up but is solid grey/blue and so i cannot open any programs. At first it was an annoyance but now its vitally imjportant i sort this out because im doing my dissertation for uni and everytime it crashes i have to just turn the power off and not close down properly. I have used a virus checker from uni but its says its clean. Does anyone have any ideas how to solve this and how i could do it in simple idiots terms.
Kind Regards Tim

