I have been using the Diamond VC500 USB capture card with my Windows 8.1 PC using Virtualdub 2 (freeware) quite happily to capture Video 8 tapes of my family to digitize them. The results are coming out great to me with no dropped frames or sync issues of any kind, even with 50-minute captures.
The trick is you need a frame-sync or TBC-like device to help stabilize the video output. Video tape is horrendously inaccurate in sending timing signals to playback devices which causes the dropped frames and sync issues when you record to a PC. TVs developed a "leniency" to these issues years ago but for some reason capture cards haven't figured it out (not enough demand?).
The cheapest way to get a frame sync device is to buy an old Panasonic DVD recorder like the DMR-ES10/ES15 and run your video signal through it. These recorders have a frame sync device in it for transferring tapes to DVD but also pass the Line In signal through the stabilizer to the Line Out port as well. I'm using a DMR-ES35 with very good results.
If you want to learn more about capturing, try these guides over at digitalfaq.com.
http://www.digitalfaq.com/guides/vid...k-hardware.htm
http://www.digitalfaq.com/guides/vid...virtualdub.htm
http://www.digitalfaq.com/forum/vide...-settings.html
They are obsessed with high quality video so often recommend devices that are over $1000 to buy, but their How To guides are a great start to learn about some new devices. Virtualdub 2 is freeware as is Avidmux to encode to MPEG. The recorders can be had for $100-$200.