WINDOWS INTERNET FXPLORER/DELETION/RE-INSTALLATION/HEADCCHE

I most of the time set Firefox as my default browser.At some point of time while unsupervised  updating of internet explorer it has been set as default browser. This option of setting default option comes during installation.When I noticed it I wanted to change it.Being a surgeon and novice in computer use I went to the menu from start and could find the option of setting the default /access program .After opening it there was option of default/custom for microsoft and non microsoft program .I instead of going to custom checked default/non microsoft  and selected firefox as default and allowed to configure. To my utter surprise till I understand what is going on my IE8 was deleted.I felt bad and wanted to configure it again from the set up already downloaded and  preserved in my system.  Then the horrible happened in form of non configuration /no icon etc.of IE8. I thought it might be due to no previous version in the system. So I un-installed IE8 whatever I call half installation , downloaded IE7 and tried to configure . My system was Windows XP Service pack3  and again it did not configure IE7. So as a desperate measure I restored the system back and found my OLD IE8 and relieved. Is not it interesting?How much neck pain I got? A lot. I posted it because it may be helpful to others to get ride of the mental and physical pain. How much of time I lost? about Two hours. And how mu