Transfer data from an old pc to a new pc?

Take a look at the Files and Settings Transfer Wizard - its built into Windows and works well see
http://www.microsoft.com/technet/prodtechnol/winxppro/deploy/mgrtfset.mspx

If you want more flexibility at the cost of being a bit more fiddly use the User State Migration Tool - There is a new downloadable version that is also compatible with Vista (don't be put off by Vista  - it also works with XP)
downlaod from http://www.microsoft.com/downloads/details.aspx?FamilyID=799ab28c-691b-4b36-b7ad-6c604be4c595&DisplayLang=en
Details at http://technet2.microsoft.com/WindowsVista/en/library/91f62fc4-621f-4537-b311-1307df0105611033.mspx?mfr=true

Depends. From XP machine to XP machine I use windows transfer files and settings wizard to USB flash drive. This works well if you want to transfer files from common locations (my docs, etc), but if their data is scattered it can be combersome to find all locations.

if you are on a network you could plug the new PC into the network and connect to the old PC - by clicking on start -> run and type in \\<computer name>\c$ (make sure the firewall is turned off) - then you can drag over the files that you want.

Good answers, same we came up with.  After testing, we have found the Microsoft solutions, NT backup does a good job backing up the data.  But restoring it is rather difficult, as it gives you a listing that is hard to read and interpret.  The File and Transfer settings wizard and USMT user state migration tool, will move the profile settings and data, but also moves all files with those extensions(ie= documents under other profiles), not just the documents under the needed profile.  But it is still a pretty manual process, have to go thru and delete each of these extensions, and specify only the folders needed.  We are not so concerned about the settings, mainly just the data, My Doc's, desktop, favorites folder, pst files, that's about it.  The third party software we tried was too cumbersome and not as easy to use.  Currently we manaully move the files usually using the method that shinatykt described.  Or with a usb drive, cd burner if available, or saving to another pc at the field location, then to the new pc when setup.
Maybe I should make this a polling question, anyone know how to set that up here?

You could just write a batch file if you are going to be moving from the same places.
below is an example assuming backup drive is e:
@echo off
md e:\backup
cd e:
cd e:\backup
md Desktop
md Documents
md Favorites
copy c:\documents and settings\%username%\desktop\*.* e:\backup\Desktop\  
copy c:\documents and settings\%username%\My Documents\*.* e:\backup\Documents\
copy c:\documents and settings\%username%\Favorites\*.* e:\backup\Favorites\  
copy c:\documents and settings\%username%\Local Settings\Application Data\Microsoft\Outlook\*.pst e:\backup\
exit

Don't have time to test right now, but see if it works

need to put quotes
"c:\documents and settings\%username%\desktop\*.*"

Almost got that batch file working.  Had to adjust it alittle.  Using usb drive, f drive, just doing favorites for testing.

@echo off
md f:\backup
cd f:
cd f:\backup
md f:\backup\Favorites
cd f:\backup\Favorites
copy "c:\documents and settings\%username%\Favorites\*.*" f:\backup\Favorites\
exit

Got all the Favorites, but none of the folders under favorites?

xcopy /e "c:\documents and settings\%username%\Favorites\*.*" f:\backup\Favorites\

Sorry

xcopy /e "c:\documents and settings\%username%\Favorites" f:\backup\Favorites\

Tried that, created the folders fine, just did not copy anything.

got it,
@echo off
cd f:
md f:\backup
cd f:\backup
md f:\backup\Favorites
cd f:\backup\Favorites
cd c:
xcopy /e "c:\documents and settings\%username%\Favorites" f:\backup\Favorites
exit

Sweet, I'll test it on some other folders too.

This is working smooth, as long as the usb drive is the same as in the script.  How do I specify, or have it prompt for the drive letter?

@echo off
cd f:
md f:\backup
cd f:\backup
md f:\backup\Favorites
md f:\backup\Desktop
cd c:
xcopy /e "c:\documents and settings\%username%\Favorites" f:\backup\Favorites
xcopy /e "c:\documents and settings\%username%\Desktop" f:\backup\Desktop
exit

AWESOME!!!, this is working like a charm.
Created two batch files, OldPc.bat
@echo off
set /p input=Enter Flash drive letter:
cd %input%:
md %input%:\backup
cd %input%:\backup
md %input%:\backup\Favorites
cd %input%:\backup\Favorites
cd c:
xcopy /e "c:\documents and settings\%username%\Favorites" %input%:\backup\Favorites
exit

And a NewPc.bat file,
@echo off
set /p input=Enter Flash drive letter:
cd %input%:
cd %input%:\backup
cd %input%:\backup\Favorites
xcopy /e %input%:\backup\Favorites "c:\documents and settings\%username%\Favorites"
exit

Still have some more testing to do, but I like the way this is working.