Need computer help. My screen resolution keeps changing every time I turn my computer on.?

When I turn it on the screen resolution reverts to 640x480 pixels. I then have to go into my settings and change it back to 800x600 pixels. I don't know why it keeps changing. Can someone please give my some advice on how to lock it in, so it won't change? Would appreciate some help. Thanks.Need computer help. My screen resolution keeps changing every time I turn my computer on.?
try going into your display setting set your res

hit apply go to advanced check to see that the

apply the new display setting without restarting

then o,k

good luck