You could write an AppleScript:
tell application "Finder" to quit
If you put that in your startup items (I think) it'll run at login...though I'm not 100%. Maybe someone else can confirm.
EDIT: this will work, but after you've written this one line of code you need to go File-Save As and choose application. Then it'll run when added to the login items.
This will be much safer than the method above as it simply closes Finder on startup