some quesitons about Ubuntu usage

[loody]

Dear all:
I use ubuntu 9.10 and I have some problem while using this version of Ubuntu.
1. my vnc connection is getting slower than 8.10.
    I used to connect XP to my ubuntu destop by vnc, and i find the
speed is quite slower in 9.10 than 8010. Did anyone have the same
problem as me and is it due to in 9.10 there is more graphic
information need to be transmitted?

2. when I activate ddd as root, I will see the error message as below:
# ddd
No protocol specified
Tk_Init failed: this isn't a Tk applicationcouldn't connect to display ":1.0"
#

But it will be fine if I activate it as normal user, like harry, the
account that I used to apt-get install the ddd.
is that the reason why harry can activate ddd but root fail because
the person who apt-get install the tool is harry?
if so, how can I add root on the list of activating the application?

3. how can I set the proxy server of apt-get, especially the server
need password and account for permission? Should I install another
package or edit come config files?

4. can I take my ubuntu as a gatway?

       A   <---->     B         <----> C
 (ubuntu)          (ubuntu)           (XP)
192.168.x.x    192.168.x.x        172.43.87.19
                     172.43.x.x

suppose I try to take B, ubuntu as a gateway such that A and C 2
networks can communicate each other.
I goolge on the net and I find some steps I have to do
    i. put 2 network cards on B
    ii. assign 2 different ip on 2 network cards on B
        (But I have no idea if there is any rule about the ip each card needs)
    iii. add route in A with the address I assign to B
     iv. add gateway ip in C, xp system, with the address I assingn to B.
but how A and C knows which package it should send to B and which not?
is there any secret in the ip?
(I am a network rookie and if the network terminology is not correct,
please let me know)

4. is there any tool I can used to change the contrast of lcd panel on
my laptop?
I can change the brightness by hot key on my T43, but I have no idea
how to change the contrast of my panel, which I can see on xp graphic
driver options.

appreciate your help,
miloody