Run asquared in safemode click here this should sort this out.
Tapping F8 on startup should get you into safemode.
If the problem persists,i would guess its logded in a restore point.
You can turn off system restore,reboot the machine,turn on system restore..... this will clear all restore points.Now providing you do not need your current restore points,i would do this.And then create a new restore point.
Before following the above,what AV found this Trojan and is it in quarrantine or a virus chest etc.