How do I keep my PC from sharing memory with the embedded video memory.

Clarifications

If the NB has it's own Video RAM it will not be sharing any System Memory with the Video as System RAM is much slower than Video RAM but if there is No RAM Set Aside For Video you are not able to prevent this from happening as it would stop all Video output.

Col

If the motherboard has onboard video and no plugin video card, you can't stop the system from using or sharing memory unless you install a video plugin card and disable the onboard video.

as both previous posters are correct, if you are looking to free up more memory there nay be a way in the BIOS.
Although you cannot stop sharing your RAM without an adapter, you may be able to 'lessen' the video impact in the BIOS. I have found often that there are several settings on some notebooks, like currently I have a 128 MB shared video, and in the BIOS I can reduce it down to 64MB. On some notebooks I have seen it able to be reduced down to 16MB.

Another suggestion, even though you arent playing games on it, add more RAM!