I don't know what a "Reinstallation" cd is.
Microsoft offers retail full installation versions and upgrade versions.
Both these come with a 25 digit key which is needed to activate them.
To get full instructions about how to create a floppy or cd to use the networking wizard and to transfer it and use it on your Windows 2000 computer go to your Xp computer (must have SP2 installed to have a networking wizard), click start/help and type in "Networking" (without the quote marks) in the box that opens.
To get the 25 digit key number for your Windows 2000 computer use it top download keyfinder v1.41 from magicaljellybean.com
That will provide the 25 digit key for your Windows 2000 system.
I am guessing that the "reinstallation" cd might be an OEM version cd or a Restore CD issued by a computer manufacturer for another computer.
Is this a computer that was custom built, or is it a brand name computer?
If it is a full installation cd, and not a Restore cd, and if the 25 digit key will work, by booting with the cd you can format your hard drive and install Windows XP if the computer you are installing it on will support XP.
Microsoft has gotten pretty good at catching piracy, so be sure that the XP key number is really valid before you remove Windows 2000.
The following Microsoft knowledgebase articles may help:
How to tell if a version of Microsoft software is legitimate:
http://www.microsoft.com/resources/howtotell/en/coa.mspx