Virtual Box on Linux….

I need to set up a virtual machine to run Windows XP and Office 07 on my Ubuntu 7.10 box. Box has 1g RAM and AMD 64 2800+ processor.

While running Virtual Box I have no plan to be switching back and forth between Ubuntu on 1 desktop and XP on the other.

I would like to configure Virtual Box to use 768m RAM while running it, but have no clue how much RAM Ubuntu will need in the background. Is this too much RAM to configure Virtual Box to use for this purpose?

Thanks!