The Registry is a little trickier. The biggest rule of thumb about the registry is: IF YOU DON'T KNOW WHAT IT DOES, DON'T DELETE IT. Though the area we are interested in is fairly safe, the bigger concern is deleting something else on the way by accident. To get into the registry, go to Start - Run, and type "regedit".
(For safety's sake, you can make a backup of the registry once you're in...that way if you made a few too many changes in there, you can undo the changes. To back the Registry up, go to File - Export , and save the backup file somewhere where you'll find it again. Make sure to choose "All" in the Export Range section of the window.)
Once you are in the registry, there are a few places to check:
--and if you are on the 64 bit version of windows--
(click the plus signs to expand the tree along the way)
This is the motherlode of programs that load without your knowledge. The tricky part is deciphering what it all means. In addition to each of the entries having a name, there is usually a path or a file name in the data section of the entry. That way, even if you don't know what the file does, you can find out where it is installed and hopefully figure out what put it there. If you still can't figure out what the entry is supposed to be launching, look for that name on the internet. You're not the first one that has wanted to clean all the junk off your computer...you will probably find plenty of web pages telling just what program put that file on your computer. The best place I've found to check what these entries do is at PacMan's Portal. Just search for the Startup item on the website, and you'll get recommendations on what you can do with that item.
So, once you've found out what the offending entry is, delete it, and it should not start up anymore. You just need to take a little more care in this area, because unlike the Startup folder, there are some things in here that CAN keep some software or hardware from loading properly. Generally, the worst that can happen is that you would need to reinstall some programs.