Scratch

Depends on what you want to record.
Playclaw is a game recorder, it probably won't work for normal screen recording. If you want that, you'll need CamStudio.

Camstudio never works for me anymore. Fraps and Bandicam are two choices(both cost money but have a free version).
Free Bandicam has a watermark at the top and can record 10 minutes
Free Fraps has a watermark too(I think) and only records for 30 seconds. So, if you want Fraps, it's no good unless you buy it or record supershort videos.
Ezvid is free, uploads directly to youtube, and even lets you add your own watermark. It's simple to use but not many features, and you have to use the music they provide and you have to upload directly to youtube. For some reason, my computer is extremely laggy when I use it, but my friends don't experience this.
Camtasia costs money but has a 30 day free trial. This is the best I've used so far, and the editing + screen recording is extremely user friendly.
My best friend uses Webinaria, which is another one, but I haven't tried it before.
I hear Sony Vegas is really good, but I think it costs money and I haven't tried this one either.

I suggest CamStudio, I have a really popular tutorial for using it  to record stuff (especially video games) on my YouTube. www.youtube.com/schnikesbro

You can use BandiCam, but I think it has either a watermark, an FPS limit, limited time to record, or any combination of the three.