Actually, I don't know of any Video Capture Software that causes dropped frames. As far as I know, the cause always lies elsewhere..

(In no order)

VV
Premiere
WinDV
SC Live
AMCAP
Main Concept MPEG encoder

and many others here and there.

I use Vegas. I have no dropped frames what-so-ever.

Droping frames are not software related. You have computer too slow or busted memory module.I have ATI for analog capture and capture trough firewire and never had frame drop since I upgraded my system.
1Gig CPU with 256M 133 should be sufficient to capture without dropping a frame.I had that before upgrade to 2.4G with 512M.
Defrag your HD and if you have 2 HD install OS on one and second dedicate to capture.The swap file could interfere with capture.

This is what I did to stop dropping frames during capture,.
1. capture to a drive that is not your primary drive
2. shut down the internet, virus scanner, messenger software
3. don't use your pc while capturing.

You could also run something like Spybot to make sure you rid your computer of unnecessary background programs that use up your CPU.

Hope this helps.

Pinnacle AV 7 (after ditching the DC10Plus card)
Vegas Video 4d

Use Canopus AVDC-1394 for capture
Capture drive is dedicated.
Catpure as DV AVI
Processor is Athlon XP 1700 (1.5 gigHz)
I'm on a dial up connection so nothing updates while I/m capturing and I dont do anything on the PC when Vegas captures a video.

My captures have not been affected by any background programs although I do not have messenger running in my XP Pro set up.

Depends on what format you are capturing. If you capture to AVI uncompressed, you will drop frames unless you have exotic hardware. If you capture AVI DV format, through an OCHI 1394 card, you shouldn't drop any frames, even if you use your PC while capturing.