Networking and Dual Boot help.

[The Wassermans]

I currently use a Dell gx240 desktop pc.  It is running XP Prof OS.  It 
is presently my primary machine and contains all of my crucial data.  
There is no space for a second HDD.  The HDD is 250GB of which I still 
have 200GB free.

I have just commissioned a second pc and have loaded XP Home and Ubuntu 
on a dual boot basis.  The PC is a Gigabyte (GA-8s648FX - 775) [ any 
comments on the M/board??].  It's in a desktop tower and there is plenty 
of room and additional slots.  This machine will eventually become my 
primary machine.  However, I am going to use it to acquaint myself with 
the intricacies of Ubuntu in the first instance.  My plan is to utilise 
the default programs immediately. And then to explore the Linux Windows 
replacement programs to uncover those I will replace my existing 
functions with as I need to use them.  Some I will initially run 
parallel.  This way I expect to wean myself off Windows.  (One of the 
benefits of Linux could become a hinderer - in as  much as there seems 
to be an infinite choice of material.)

In the short term I expect plenty of frustration and a big investment of 
time as I climb the learning curve.  I don't have the inclination to be 
sat in front of my computer beyond what, for me, is reasonable.  I have 
several other priorities which will also compete for my attention.  So I 
am going to rush ahead slowly.  (Too slowly, I fear, for some of the 
dedicated list people.)  I want to be fully Ubuntu'd by the end of the 
year.  It might well happen sooner.

Okay, enough talk!  So I can get the ball rolling, please will help me 
with the following:

* How best do I set up for Sharing files on a dual boot system?  If I 
edit a Windows data file in Ubuntu, will Windows be able to read the 
modified file?

** I believe I can run Ubuntu within Windows?  What/where is the program 
for that?  The idea is to toggle between XP and Ubuntu to compare 
certain features.

*** How do I go about Networking between the two above PCs?

Inevitably, this information is available on the net.  I know.  But  . . . .

 I look forward to some of the selfless help and advice provided by this 
dedicated community. Thank you in advance.

Regards
Dave W