How to edit my Nikon D5100 videos?

When I try to edit the video from my Nikon D5100, it is incredibly slow and stuttery in whatever video editor I try to use. If I convert it, the quality gets significantly degraded. Is there any way to fix this?

Added (1). Sorry, I should have mentioned that. It's a PC with 4GB of DDR2 ram and Core 2 Duo processor. I haven't had trouble like this editing videos on it before. I tried on my laptop which also has 4GB of ram and a Core i5 processor. I have edited videos without trouble on both my machines, so I'm thinking that it is the format of my camera. That's why I now wonder if there's format I can convert it to that still looks good while actually allowing me to edit.

Added (2). No, I haven't edited HD on either of them before. That must be what my problem is.

Adobe elements - movie editor
windows movie maker

It seems that your computer is too slow. For HD video, you will need a dedicated graphics card.

mind telling us what computer you are using?

edit: have you edited full HD video before on your machines? I know you can do video on laptops, but when it comes to HD video they get laggy and basically what you describe.

I'm not well versed in video formats at all, so I can't help you there.