Note that upgrading over Windows ME usually results in significant problems.  You really should do a clean install, which involves reformatting the hard drive and then installing Windows, device drivers, and application programs, and then all data files. 

First go to the Dell download site and download all of the Windows XP compatible drivers for your system.  Note that many of the XP drivers for the 4100 are native to  Windows XP, but some may not be, so it is better to be safe and have them already available in case you need them.  Put all of these drivers on a CD-R so that you will have them when you need them.  Second, you need to back up all of your data files to CD-R or some other removable media.  These would be things like pictures, movies, e-mail, internet favorites, word processing documents, spreadsheets, etc.  Third, you need to locate the CDs for all of the programs you want to install.  After the reformat and installation of Windows XP, none of your programs will be there.  So make sure you have a means to reinstall all of your programs.  

Then, see the following site for instructions on how to do a clean install of Windows XP:

http://www.djdenham.com/Install%20Procedures.htm

Steve