If you used the installer version of XAMPP then in XP often this will give issues that seem to be unexplainable.
Try uninstalling XAMPP and then use a different method, ie. the zip version, instead.
These instructions may help you along the way:viewtopic.php?p=179699#p179699
Before deleting the xampp folder it is very important to make sure that all service ticks in the control panel are removed, all components are stopped and the control panel is also shut down and not simply sent to the system tray.
Using this zip method has been known to fix many unusual issues that have been associated with the installer used in XAMPP and is why it is possible it will be changed in the next version of XAMPP -> 1.7.8
Item 4 viewtopic.php?f=16&t=48373#p185650