OK, I'm not a registry expert, but that looks a little strange. "HKEY_CLASSES_ROOT\HKEY_CURRENT_USER" should be one or the other, in this case, I suspect it might be "HKEY_CURRENT_USER\Software\Microsoft\Shared Tools\". I have checked that entry on my own PC, and I don't have a MSConfig folder in that directory of my registry, so I would guess that it shouldn't be there in yours. Are there any other items in that folder, other than "startupreg\slk563a7"? The
real MSConfig folder should be in "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Shared Tools\MSConfig\startupfolder". If you check on your PC, you should find it there, with all the genuine startup entries.
I think it would be safe to delete the "MSConfig\startupreg\slk563a7" part of the registry entry you found, but as I said above
back up your registry before making any changes, then if you find problems afterwards, you can restore it to how it was.
You might find the following program useful, but as the item you found isn't in the correct place, I'm not certain that this program would clear it.
http://www.get-in-control.com/msconfig-cleanup/You could also try
www.hijackthis.de, which might be a safer way to remove the item without manually fiddling with the registry. Download and run the file, and if your startup item is there, tick and remove it. You can also send the logfile for analysis if you want to see what other nasties might be lurking.
Good luck!