If you run a pc emulation software such as MS's Virtual PC, or VMware etc,

what impact does the physical operating system have on it?

For example, if on your main os, you have a virus or key logger, would it be able to log on the Virtual PC also?

and does the Virtual PC actually use it's own ram, so for example the main os couldnt include info from the virtual pc in its page file etc?

Any advice appericated.