I could be a number of things.
The suggestions so far mention a graphics card. This is an obvious conflict. You may want to check that out in more detail.
In the event that you have already done so, then I suggest you check your Windows registry settings. Conflicts always occur with Windows and its internal settings. There are few key settings that you can check out with the Systems tools already built into Windows.
You may also check out software that can do these checks for you and will tell you what conflicts are on your system. They tend to fix your computer in 1 click.