Ubuntu 10.04LTS IP Address thru proxy changes

Good day folks,
Firsly I want to thank all fer aproviding me with the answer to my initial questions(s) on networking 10.04LTS, which by the way went well on the first machine that I installed.
I do want to know more about this though : we have static IP

(a) the machine installed with 10.04LTS(note: initial install was XP) located in the general area of the office, thru CCProxy had an IP address of x.x.x.32, and after the instal of Ubuntu, the suffix changed to x.x.x.35 - and hence could not get internet/connect to server, but this was easily remedied by editing the address of the machine on the proxy side to x.x.x.35
(b) when the machine was then relocated to the personnel department, that suffix changed to x.x.x.22 - again this was solved by editing at the proxy side.
(c) i have 3 more machines(XP) - which will be re-installed with Ubuntu 10.04LTS, an as an example : if the machine had an IP address of x.x.x.188 going thru the CCProxy, after installing Ububtu 10.04LTS would i encounter the same change of the IP address suffix? and/or if the machine(s) are moved about the office, will the suffic change accordingly?
(d) fer me own knowledge/understanding - could someone please assist explain why this happens or maybe even what i am doing wrong.
(e) also is it possible to change the suffix that was generated to read thru the original inidicated/setup initially thru the CCProxy?
My thanks and appreciation in advance fer the help rendered.
James R
email: <email address hidden>