Trouble with Flashplayer 11.5 installation

"User does not have sufficient priveleges to install AFP." I am signed into Windows XP as the "Owner" and have never had trouble installing anything before. I have Avast antivirus , and have temporarily disabled it to no avail. Any help would be SO appreciated!!  In the process of running the update, it apparently uninstalled my old version, so now I have no player at all!!