Good Softwares

Office: Open Office, this is an free alternative to Microsoft Office and can handle MS office formats as well.

CD/DVD Writing: InfraRecorder, this is a free alternative to Nero CD/DVD burner.

PDF Reader: Foxit PDF (Tabbed PDF browsing and Fast), this is not open source however it has a free version as well. Open source Sumatra PDF is good and very fast, however it is still evolving. I was very impressed by the speed and shortcuts similar to Vim.

PDF Printer: PrimoPDF, this is not open source however it has a free version as well. This is best for Windows OS, I have used open source alternative PDF Writer however I am not impressed.

Media Player: Vlc media player, its open source and the best in comparison to proprietary softwares as well.

Image viewer: ACDSee, this is a proprietary software. I tried some open source alternatives and they are no were in comparison to this. It is my personal opinion there might be some good ones that I would have missed.

Compression tools: 7 zip is open source and almost hadles all format zip, rar, tar, .bz2 and .bz etc, the best.

Audio Recording and Editing: Adacity is open source and its very good. This also does conversion to mp3 (additional LAME MP3 encoder dll needs to be copied). If the system powers off / software crash, recovery of the recorded audio is possible. You can look for more info on net.

Editing: Vim - I feel this is the most powerful editor in the world, if you are not familiar with Vim and more used to windows like editor then Notepad++ is another good option.
Unix Emulation for Windows: Cygwin, the best.

Comparison Tool: WinMerge is a good comparison and merge tool. Araxis Merge is a proprietary software and it does much better job than other comparison tools, I prefer this personally.

SCP client: WinSCP, the best.
FTP client: Filezilla
Telnet/SSH client: PuTTY & PuTTY Connection Manager, the best.

Chess: WinBoard with GNU Chess is a good option. If you are a serious player then Fritz (not free) is the best.

Visit: www.osalt.com to check for Open Source Alternative for your proparatory software. Also www.opensourcewindows.org is also a good place to look for Windows open source softwares.