Well it may be you have been attacked by internet security 2010, only one program seems to flush this mess off an infected system, try www.loaris.com.You may need to run this and restart several times.This trojan
disables regedit, and runs several startups which you can see with cc cleaner.
Regain use of regedit with gpcedit in the run bar. this is ieasily googled. when you get to regedit try find "sdra" AND DELETE