Slow down PAL NES games for use in NTSC console?

[Rockard]

The problem is this:

I live in sweden, a pal region. And I have for some months collectected about 100 nesgames in pal.

Now, I just recieved my NTSC US NES so I soon can perform the RGB-thingy-playchoice-trick.

But, now nearly all my PAL-games run too fast in my US-nes. I totally understand
why the case is this( the games are adjusted (speeded up) for pal), but is there some way I can
slow the game down, maybe use or make some kind of converter, so my games will be fully ntsc compatible?

Are the actual romcode in the nesgames adjusted for pal, or is it just some generic chip that makes this?
If this is the case, I feel something can be fixed.

I want to enjoy my games in wonderful rgb, but just don't feel like buying all games again in NTSC format..

any comments, suggestions, facts appreciated..