It all began by upgrading to XP (from 2000)...
Athlon 1000
768Mb ram
Matrox Millenium G450
I've defragged, tweaked WinXP with the help of www.blackviper.com (lots of info there, by the way). My drive is used at 10% capacity. I tried capturing tapes shot with both "normal" and "progressive scanned" modes on camera (different physical tapes), I set my RAM buffer at 512 (I got 768Mb total memory), I checked-unchecked the "custom frame rate" box in VidCap4.0 - Options - Preferences - Capture tab ...
My last "result": 107 dropped frames after less than 60 seconds of capture. Horrible to see and hear...
I don't know what to do more.
Do you please have any idea? I've spent the whole day up to now on this problem ... :(