Is this the problem you're referring to bonescitgo1?
If so, yes, when Windows is reloaded sometimes drivers are lost. (They aren't actually lost. The address to them is)
Dell Support > Dimension 2200 Desktop PC > Downloads,http://support.dell.com/support/downloads/driverslist.aspx?c=us&cs=19&l=en&s=dhs&ServiceTag=&SystemID=DIM_PNT_CEL_2200&os=WW1&osl=en&catid=&impid=
Page comes up automatically to Windows XP operating system. (You installed WinXP Pro)
On this page scroll down to the heading - Network (17) and left-click on the blue down arrow to the left.
There are two drivers listed for an Ethernet adapter;
1) GVC - Driver - Ethernet 10/100 PCI Adapter
2) Intel - Driver - PRO 100/M Ethernet Adapter
To know which Ethernet adapter is in the computer go to Device Manager.
A) Left-click on Start
B) Right-click on My Computer
C) Left-click on Properties at the bottom of the list.
D) Left-click on the Hardware tab
E) Left-click on Device Manager
When Device Manager loads left-click on the + sign to the left of -
Look at the manufacturer name. It should be either GVC or Intel.
Close all windows, (Device Manager and System Properties), go back to the desktop screen.
Now go on the internet, and to the link above.
Left-click on Download in the blue oblong circle, to the right of the appropriate driver file, GVC or Intel.
The Download Options window will come up.
USE the bottom option; Download via your Internet Browser.
Left-click on Download in the blue oblong circle, at the bottom left.
A small window will come up on the right; Opening R35845.EXE
Left-click on Save File.
Another small window will come up on the left.
In the wording at the top of this window, tells you where the file will download to.
Suggest you write it down.
It may have Desktop, or My Documents, or Downloads, in the wording. (Windows XP)
1) Desktop: The file will be on your desktop screen.
2) My Documents: Left-click on Start, then on My Documents
3) Downloads: Left-click on Start, then on My Documents. DOUBLE-click on Downloads.
When you see the file DOUBLE-click right on it. The Installation Wizard will come up.
At the bottom of the first small window left-click on Next.
Same with the second small window.
Left-click on Finish on the third small window.
[ DO NOT change any settings in the second window. Windows knows the proper place to put this driver file ]
After the Installation Wizard is finished, close all windows, go back to your desktop screen, and restart the computer.
When Windows loads all the way, you should get a pop-up out of the system tray at the bottom of your desktop screen,
"Found new hardware", and perhaps another one will follow, "Found XXXXX Ethernet adapter"
(XXXXX = the manufacturer name of the Ethernet adapter)
For additional questions please post in a Comment.
(Hope things start looking up for your friend)