KB914882 problem

Hiii...

I wanted to install Microsoft Security Essentials (since the already exisiting anti-virus software took up a large space)....and it asked to download Microsoft Filter Manager KB914882....and I installed it successfully....but there started the PROBLEM...!!! Now I am not able to do things I want to do...not able to connect to the internet...USB device not being read...and Administrator problems and so on.... I did all this on my Local Computer that is directly connected to the Internet Router....
and I am able to connect to the Internet on my sister's laptop...
PLEASE HELP ME...!!! :'(

Thanks in advance... :)