by Ken Task.
Am a Linux guy myself, but this should do even on Windows ...
find your php.ini file and open with NotePad. Find the line that has max_execution_time = 30
change the 30 to say 160.
Save the file.
Restart Apache.
Try in the install again.
Might want to read the release notes:
http://docs.moodle.org/dev/Moodle_2.5_release_notes
'spirit of sharing', Ken