Helpful Programs & Codecs:

Packer:
Powerarchiver
Winzip
WinRAR
hkSFV

Player & Codecs:
Windows Media Player
Real player
Quick Time
Winamp
Elecard Media Player (MPG-2 Codec)
DivX
XviD
Nimo Codec Pack

Download-Manager:
FlashGet
Streamdown
Net Transport