Click on Run one time, then you'll see all programs that starts when you're computer is starting in the right window. If there's something you don't recognize, you shall delete it by selecting the file and hit Delete on your keyboard. For Back Orifice / Netbus the names of the files can be just .exe, patch.exe, catch.exe, or musse.exe - the file is spread under several different names. If you're uncertain of what belongs in the right window you shouldn't remove anything without consulting someone who knows their way around computers. Example of program which absolutely mustn't be removed is SystemTray (SysTray.exe)
Then click on Runservices one time and in the same manner remove all in the right window which you do not recognize.
Close Regedit by clicking the cross in the upper right corner and restart your computer.
You have now removed Back Orifice and NetBus from your computer.
In the future, remember to be careful when downloading unfamiliar files.