Icons change to google chrome icon without program

Hello,
Why do the icons including those which are "none opened or started" and many non-relevant icons get access by #googlechrome to be changed to the #google-chrome-icon without permission from the computer user?
While using public access internet via a pc running xp the user then gets to choose which internet browser or browser to use.. I always use Firefox running from portable apps.
SO UNSURE HOW ALL MY ICONS ON MY PEN DRIVE ARE NOW BEEN CHANGED BY THIS GOOGLE CHROME WITHOUT EVEN STARTING OR RUNNING THIS PROGRAM.
Am aware that maybe its part due to using XP but this is a public access internet within the UK, how has Google managed to do this?
How can I now access my files on my pen drive "includes my own designed web page temps, spreadsheets, pdf type files without them trying to redirect my own internet at home or in the office"
Something is'nt right....
Hope this is'nt a problem for the future and happy for any advice to prevent this...
Many Thanks