I know, there's a ton of zip libraries out there. And some are actually free, though, typically, those come with some pretty onerous licensing if you intend to use it in a commercial product.

.NET has some built in zip support I believe, but if you're still playing in ActiveX land, one library to check out is FathZIP.

It's 79$, is fast, seems very stable, and, the kicker, supports completely in-memory zipping and unzipping, so you don't actually have to save a file as a temp file just to uncompress it.

Oh, and did I mention it's 79$!