I installed XAMPP on a fresh Windows Vista Business Ed. Worked fine until i rebooted after installing some updates...
Trying to start apache from the XAMPP control panel was causing a blue screen of death (related to win32k.sys driver)
A workaround i got from the german forum thru google.com/translate was to start apache using the batch script
where XamppInstallDir on mine was default C:\xampp
Hope this helps someone else