There's virtually no need for klite codecs on Windows 7. It supports mp2,h.264/mp4/avc,divx,xvid etc out of the box. I really very strongly suggest you don't install it.
The only things you might want to add are an mkv splitter and maybe flac if you use that at all.
I found Windows Media Player out of the box to be pretty poor at playing back videos, it will randomly stutter through a video instead of playing it (yet often it will play the same video with no issues). It also doesn't include all of the codecs I need for some of my videos.
So my install list:
- NetBeans
- SciTE (better then Notepad++)
- FileZilla
- Tortoise SVN
- Process Explorer (daaaamn useful!)
- Powershell (although this now comes with Windows 7)
- The Gimp (the UI is actually really good on a dual-screen setup, who knew!)
- The Combined Community Codec Pack, including Media Player Classic Homecinema
- Avast (used to use AVG, but it gave me too much hassle)
I'd also like to mention VS, Eclipse, Paint.NET, ColorPic, Expression Design 2, Spotify, Folding@Home, JEdit and WinDirStat.