Run \xampp\xampp-portcheck.exe to find out what is using the ports that XAMPP needs exclusively.
Often it is down to Skype and can be corrected by configuring Skype to use ports other than 80 and 443.
The other culprit and more the likely one in a Windows 2003 Server is IIS (Internet Information Services) which can be disabled in Windows Add/Remove Windows Components or similar location.
You can't run more than one application server on the same port and Apache uses ports 80 and 443 exclusively.
BTW, in future and for faster responses, you could use the XAMPP For Windows English forum:viewforum.php?f=16
Good luck and best wishes.