as a novice in the world of computers i have relatively little knowledge of malware and othe things like it but after accidently installing some codec thing off of a video my brother was attempting to watch ive been landed with this trojan. ive never had one before so any help someone could offer with regards to getting rid of it would be greatly appreaciated.

it causes some weird dialogue box to pop up telling me ive been infected and need to clean the system immediately...

thanks ina advance