Sharing folders between 2 guest OS (Win-Linux)

[qiGuar]

Hello. My primary OS is Windows 7.
I have Windows XP and ubuntu as guest OS.
I need to share a folder between my guest OS directly.
How can i do this? Haven't found any information and can't resolve this problem for about a week((
Please, write full tutorial or where can i find it? I will provide any information needed to help me.

[Perryg]

Chapter 4.3 Shared folders in your VirtualBox users guide

[qiGuar]

No, it's not what i want.
I already shared folders between Win 7 and guest OS.
Now i need to share folder between ubuntu and win xp directly.
For example: i have folder "123" on win xp(guest os) and i want to access it from ubuntu(guest os). and vice versa.
that's what i want.

[Perryg]

Then you will need to use a network share.