A Suspicious Script

My PC is attacked by a Suspicious Script called "NTDETECT.exe" which is harming my PC's parformences. It's symtom is when i double click on my disk drives to open then cz of this script drives dont open. Instead my virus guard notify me about this script. It also denies me to unplug any removable drive. Can anybody tell me how I could get rid of this without formatting my HDD.
I would be grateful.

Process File: ntdetect.exe or ntdetect
Process Name: Trojan.W32.Small



I'd suggest following the instructions in this post:

Read This First - IMPORTANT Instructions

Then post a log on that (DAL: our sister) forum as the current log reader here is on leave.