Well, it also depends on how strong your system is.
If you have a REALLY powerful one,then
KGB archiver might be interesting.
(not to be mistaken with the spy/ad ware KGB)
if you don't have the requirements for KGB, then
7zip would be a good second.
Still needs a good machine, but not as much as KGB.
Also need compatibility with a huge amount of other file compression techniques?
Then you should go for
WinRAR. Supports ALMOST all extensions.
(.KGB isn't one of them....)
This is the best one of the Very Well Known Compressors.
As a last suggestion I would advise you to take a look @
WinZIP.
OK, I know. It not even closely as good as any of the above archivers, but it DOES have the BEST windows integration.
(as in, windows XP and above can open .zip files as if they are just folders)
Hope this will help you in making YOUR decision.
I just consider this as just hints and tips.