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i have an winxp guest on my ubuntu host (vbox 2.2.2). network used via NAT mode. i have LAMP runnig under my host system. LAMP is configured to work with localhost. can i somehow access these services from guest system?

This has been asked a LOT. Switch to bridged mode or else use port forwarding.
Try Googling this on the Google.com with site:forums.virtualbox.org at the end of the search string. It will help you find most of your answers.

Of course you can access them from the Guest. Connect to 10.0.2.2 to get to your Host. Keep in mind, that when you set everything for Apache and MySQL to listen only to localhost, no other system will be able to connect to it.